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Gaining Focus - Upgrade, mod, or replace?


Fo_Cuss

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Have you ever paused, and wondered...
How would I cut plastic tubing, if I ever needed to?

If so, you probably dismissed the train of thought, assuming that at some point in your life, you would discover the answer to this conundrum.

Ha!
The wait is over...   :angel8:

Cutting the 'Lens Mount Assembly' Components

Two items required cutting:

  • Grease tub base - removal
  • Lens holder adapter - shortening

Grease tub base - removal

First step was to mark out the circle to be cut, using a drawing compass.

The base already had a centre punch hole.
Rotating the work piece is easiest, when possible.

Sharpen and strop (to scalpel grade), a small kitchen knife.

The grease tub plastic is very soft.
You cannot simply push the knife through, because once started, it would slice through the plastic like butter.
... running away at a tangent from your circular guideline.

Instead, take your time, and just penetrate the plastic (on the line) with the tip of the blade.
 

Cut_plastic_base.jpg.3cc063fc76ba7d52f88b601c2ed1394b.jpg


Using that point as the fulcrum ... arc the knife, forward and backwards, following the line on the forward movement.
This 'arcing' of the knife will cause it to cut through the plastic in a controlled manner.

Keep repeating this rocking movement, and work your way around the circle.
Of course, you are going to fail ... it's cuting sooo easy ... whoops!

However, if you are following the procedure, the fail will be inconsequential.
... simply pick up your line, and keep going.

In less than five minutes, the job will be done.

Here it is, with lens, offered into the lens holder adapter.
It fits !  😅

Cut_lens_holder_in_adapter.jpg.52b539f57b728d0e7ae1dd237f791859.jpg


What I would say, when cutting into a radius
... I would recommend cutting to a slightly larger diameter - say 91 mm for 90 mm required.

No matter, I can tidy this; but that task will take far longer than simply cutting it right in the first place  😉

Problems ... or are they?

My goodness, the lens is a tight press fit.
This is due to the grease tub slightly narrowing towards the radius - it's a manufacturing thing.

The plastic diameter is ultimately enlarged - it stretches.
Same goes for the whisky cylinder, when pressed in.

Actually, once the lenses are in place, they will be going nowhere.
There would be no need for the whisky cylinder to lock the lenses in place.
However, that cylinder is still needed, to provide a base for flocking.

The grease tub can't be flocked, as the lenses would not go in.
The only part of the grease tub that requires flocking, is the radius area.

The white plastic around the lens edges will be masked by blacking the lens edges.
Fine!

Assembly will involve warming the grease tub, to aid insertion of the components.

Final adjustment of the lenses to achieve perpendicular, will have to be done by simply applying pressure to the high side.
... they may anyway be forced to assume a perpendicular position.

Cutting the lens holder adapter

As with the soft plastic base removal...
This task also requires a specific procedure, if the cut is to be perfectly square.

In order to measure where to cut the adapter, the lens mount was assembled
... and why not? ... I placed the assembly onto the 100 mm scope tube.

hahaha ... an early morale booster, seeing how everything is coming together  😀

Lens_mount_initial_assembly.jpg.37d000873f0a723d0d3c646901bc11ba.jpg


From the image, you can see that I would drop the vernier depth guage from the top of the adapter, to the top of the lens holder.

Upon disassembly, the cap thread depth was measured, and together, I had the cutting dimension.

Marking off, was achieved by setting the vernier guage to the amount of tube to be removed.
The top vernier jaw was placed on the top face of the adapter, and the lower jaw tip was pressed into the the tube plastic.
The adapter was then rotated, and steadily a line was scribed around the adapter tube wall.

Now the cutting.

You can't simply cut through with a full size hacksaw (in truth).
It is possible ... I could probably do it; but it's not the method.
Think about it...
Just supporting it is a nightmare.
... as would the cutting, because you can't see both sides of the tube
... the tube walls would begin to flop around
... the hacksaw blade would walk; and you'd be left crying, thinking of what might have been  🙁

No; the way to cut such a tube, is to use a junior hacksaw.

Supporting the adapter on sand (and holding it with your left hand) would be ideal for the beginner.
I just held it on my table, and managed the rocking (as the blade cut).

The objective is to gradually cut a slot, all around the tube.
... until the slot begins to break through the tube wall.

Tip ... a worn hacksaw blade really helps.
Even hard plastic is soft to a hacksaw blade, and new teeth will grab.

The worn 'middle two-thirds' can be used to graze out the initial slot (rotating the tube inch by inch).

Once a guide slot has been created, continue cutting, but push the blade further forward.
The worn blade rides in the guide slot, and the unused part of the blade feeds perfectly into the tube wall - without grabbing.

Continue in this fashion, regularly cleaning the blade - otherwise, the plastic swarf binds the blade.

Part way through, this is what it should look like:

Partially_cut_lens_holder_adapter.jpg.e994ebadcefb4cda39ed759556b684e7.jpg


At some point, the blade will begin to break through, and possibly grab.
... rotate the piece, to find sections that need further cutting.

Looking on the inside of the tube, you will see if the cut is almost through the entire circumference.

You can take the sharp knife that was used earlier, and either seperate the pieces, or cut enough to allow the hacksaw well into the tube.
... a few strokes, and it's in two pieces.

Place a large sheet of emery, at least 150 x 150, on a flat table, and rotate the cut face on the emery, with light pressure
... until satisfied 😀

Finish off, with folded ultra-fine grit paper, pulling the tube edges outwards, to remove plastic strings.

The end result should look like the piece has been cut on a lathe:

Cut_lens_holder_adapter.jpg.276e1d9dd36f4dc3d1baa4f7d74b215d.jpg


Lens Mount Assembly - 1st View (in the nude)

Lens_mount_assembly_1st_view.jpg.9341d503fd49699b09f510ef6fa0ced5.jpg


To me, this is looking great
... but I can understand why, to the casual observer, it looks naff ... the gaudy red lens cap doesn't help.
Though let's face it ... very few of us look good in the nude...

Dressed, and a bit of lippy, and she is gonna be a stunner  😁
 

 

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Stainless Steel Adapter Cut

The 'exhaust tailpipe tip' arrived today - 63 mm - 102 mm adapter.

Looked nice, as an exhaust tailpipe tip, but the welding wasn't perfect.
... however, just good enough for my purposes (thankfully).

60 mm Tube Connecter

The first problem was that the OD 63 mm, turned out to be 67 mm.
This meant an ID of 65 mm.
Not great at all, as I have 3 mm to make up  🙁

The options are: Fibreglass sheet, or tin can wall.

It made me research steel tubing.
63.5 OD - 60 ID is a standard size, only it is not stocked locally - so I scrapped that idea.

I resolved to await the laser calibrator.

100 mm Tube Connecter

It wasn't cylindrical - the weld and seam had pulled it oval.

I wasn't worried, as the vice could sort that
... but the first task was to cut off the rolled end.

Placing it on a marble table; with an appropriate tin can, to hold the marker
... the piece was rotated, and marked off.

Unlike the plastic tube; this piece could be held in a vice, and a new blade was installed in the hacksaw.
As with the plastic tube, a guide slot was first cut.

Breaking through, is best achieved by cutting the nearest side of the tube - avoiding the far side.
This allows the teeth to cut into the circumference, rather than meeting the steel wall edge.
The piece is gradually rotated and cut, until the pieces separate.

The dangerous steel strings, and sharp edges, were removed, before cleaning the face on a flat square of emery.
It was then taken to a circular form, by squeezing the high points in a vice.

It wouldn't slide over the 100 mm tube ... but it was almost there.

The inside was cleaned up with a small grinding wheel, and the edges were chamfered - as were the plastic tube edges.
... and this time, it could just slide on (press fit).

Perfect!

Here is the finished adapter :

Stainless_adapter_cut.jpg.028edf98aebd4f39e8abc35d26f18df3.jpg


The image seems to show the 100 mm section to be tapered, but it's not.

Weight = 286 g
Lens mount assembly, currently = 700 g
100 mm PVC tube = 1070 g per metre.

Consequently, the scope front end is likely to top out around 1.3 Kg

Rebalancing of the scope, will be required  🌝

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New Arrivals (and a surprise)!

Laser Collimator
Datyson 90 Degree Diagonal Zenith Prism
Celestron Omni Plossl 2x Barlow
Celestron Omni Plossl 12mm & 4mm Eyepieces

Plus, I was gifted a :
Celestron Plossl 6.3mm Coated Eyepiece

Celestron-Plossl-Eyepiece-6-3mm_cut.jpg.b2da74d8c6578e0d991205b18861d778.jpg

Ha!
Now that's what I call "a good packing material" 😁

The external cardboard box was sound
Inside, each component was individually very well boxed.

The Laser Collimator and 2" adapter, has a strong storage box ... the components supported in a velvet type injection mould.
Very good.

Note: The Laser requires a CR2032 3V button battery (which I had in stock) 😉

While the simple Plossl appears to be well made - blackened and coated...
The Omni series has a real quality feel to them - a step above the basic Plossl..
They may not be comparable to some of the high end eyepieces, but for what they are, they are well made (from a visual perspective).

Of course, the proof of the pudding...

Plossl vs Omni Plossl vs starter Kellner

I think that it is upon me to carry out, and record, some comparison tests.
Having checked out YouTube, there is a lack of comparison records at this 'initial upgrade' level.

Thankfully, the scope can still be reassembled in it's 60mm format.

A test such as this, will then provide a baseline of optical clarity; from the true starter scope ... through stages, upwards to a 'pro' 😎  90/f1000 refractor scope.

The Test
I envisage using some wind turbines that I know are 10Km distant, and viewable from my location.

A planetary, or celestial test is unlikely to be feesible
... having to manage multiple lens changes within both the scope, and the camera, whilst chasing objects that require focussing
... all that, in the dark.

Er ... No!
A static object, with the scope locked down ... will enable genuine comparisons to be made.

My starter Kellners are : 4, 9, 12.5, 20

This will allow direct comparison with the Omni 4mm and Omni 12mm (close enough).
However, I will take images through each of the lenses, including the Barlow modded magnifications.

This will provide a direct comparison between a Barlow 6mm and a Plossl 6.3mm
It will also be interesting to see a Barlow image at 2mm and 3.15mm.

Then...
Once the new scope has been finalised; the test can be repeated.

My goodness ... the results had better be a major improvement 😅

 

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Collimating a Refractor Teslescope (using a Laser)

The laser collimator is primarily designed for use with reflector scopes.
However, when assembling tubes, it was clearly going to be indispensible.

My basic plan was to use it to centre the objective lens to the eyepiece
... and see what else fell out in the wash.

I first carried out some freehand testing, pointing the laser beam through a lens.
This was very useful, as I discovered that when the lens wasn't square; two additional 'planetary' dots became visible.

Flushed with this important discovery, the scope was reassembled.

The immediate concern was the oversize internal diameter of the focus tube eyepiece mount.
It has a finger screw clamp, but this would push the eyepiece to one side.

I carefully applied plastic electrical tape, to the tube interior.
By, a stroke of good luck, this produced the perfect ID.
(I'm of a mind to lock these strips in place, with a laquer, so perfect are they)

The next concern has been long obvious to me...

The focus tube assembly is held in the scope tube, by just 3 screws (passing throught the steel into the pastic mount).

Focus-tube-3-screws.jpg.1d2cef698e6bd4fc274f8f541b35d5a0.jpg


It simply isn't enough ... a total of 6 screws are required.

Similarly, the objective lens mount ... though that will be anyway ditched
... but it only has 2 fixing screws.

Lens-mount-2-screws.jpg.502655cbfb6603a2f4f672e0c62d5323.jpg


Note: They are tapered screws, so if malfitted, there can be no adjustment.
However, I pressed ahead.

Collimation

The laser provides 7 settings.
1,2,3,4 is a circular beam of rising power.
5,6,7 is a short 'bar' (or slot) beam, also rising in power.
(Excellent!)

With the collimator in the focus tube, I managed to centre the focus assembly to the objective lens.

Here the photon beam can be seen impacting the len surfaces:

Lens-dots.jpg.f0cfb78ef43146b9d3891474a8291285.jpg


... and here it is centred against a paper screen:

Les-paper-centred.jpg.f95431e3f7ec1d5495b7a2f24fc62ad5.jpg


Ha!
What I hadn't realised, was that the beam would also be reflected back down the scope, directly onto the collimator target area:

Collimation-1st-dots.jpg.fa0add8d83e3b7c4c1bbf15ec51af63d.jpg

Above, the bar can be seen to be almost directly over the centre hole (through which passes the laser beam)
... but also present were two planetary dots of light.

As you can imagine ... I was more than a little impressed by this laser collimator.

Next, I wanted to see what would happen, when the Barlow 2x was fitted, and within it the laser:

Collimation-with-Barlow2x.jpg.e18922c5a5062df35fb44519d4376f33.jpg


On close inspection, the bulk of the light is focussed plum center, though there is a light glare in the top left quadrant.

At this moment in time, I don't know enough to precisely understand what is happening.

Obviously there has been a focal length change; but...
This was not a strict test ... things were touched and changed (to see the effect)
... and the Barlow is an utterly perfect fit in the focus tube (penetrating deeply).

Reflections from a successful test...

Reflector scopes regularly decollimate.
For this reason, they can be easily adjusted back into shape, by the supplied adjustment screw system (and a laser).

Refractor scopes, traditionally have no such adjustment.
From this, I sense that maladjustment of the lenses may be better tolerated (tell me if I'm wrong).

Either way, it is only logical to assume that a well collimated refractor scope will provide superior performance, to one that isn't.

Because of this, I may need to create an adjustment system for this scope.
... a system that enables screw centering adjustment, prior to clamping, and permanently fixing.

Something to think about, whilst I bask in the warm glow of 'knowing that collimation will be achieved'  🌝

 

Edited by Fo_Cuss
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Onwards and upwards!

A centre spotted paper target over the front of the objective - the laser spot should hit centre......

I also use a Cheshire collimating tool - illuminate the side and look at the reflection doughnuts at the objective. Ideally they should be uniform and concentric.

That's as good as things need to be.

Suiter's "Star testing Astronomical Telescopes", p122

 

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Thanks for those welcome words of encouragement,and advice, Merlin :)

However, it has come to pass, that the fundamental errors in the lens industry must be addressed.
From an Engineers perspective; sadly, this is an all too normal event
Take an object, and berate the design team (head of design), for not fixing a fundamental problem ... that is easily fixable.

In this instance, one of the deeply fundamental issues is concentricity.
It is at the heart of lens design
... particularly where lenses are joined together, such as an eyepiece to a telescope, or an eyepiece to a Barlow.

There are two ways to deal with this issue to gain accurate concentricity:

  • The expensive, difficult (silly) method
  • The low cost, simple (sensible) method

Guess what the lens industry chose?
They chose to use 'sliding fit' OD/ID interfaces - the expensive, difficult (silly) method.

This method can work, only that the manufacturing tolerances must be very tight
... in the region of 0.02mm of clearance.

This is not feesible for an aftermarket industry of interconnecting lenses.

The solution chosen, was to simply increase the tolerances
IE. Make the female element large, and the male element small.

From a production perspective, this is an inexpensive solution, as there is hardly any scrap.
Only that, from a user perspective, the male element just flops around
... and over a distance of 700 - 1000mm, the two ends are not concentric to each other.

This is exactly what we don't want, when building a telescope.

The Easy Solution

Use tapers!

Tapers are cones - male and female.
They self align perfectly.
They also possess self-locking characteristics
... yet with a twist can be easily unlocked, given they are finished similarly to as they are now finished.

Further; and most importantly ... they can be introduced into a market of sloppy, sliding fit lenses.
(if either element lacks a taper, the interface becomes the sliding fit).

Further, and also of critical importance ... dimensional accuracy is not required.
The machining angle must be set, but this is anyway programmed, or copied from a pattern.
Dimensional accuracy is a function of 'cutting' (less or more), and dimensional control.

For joining lenses ... taper dimension control is irrelevant
... if the taper is a little forward, or back; it makes no difference, because the scope must anyway be refocussed after a lens change
... and even broad tolerances would produce imperceptible differences in this area.
(unlike sloppy sliding fits, that produce wild concentricity errors)

What? ...
You are thinking that a taper sounds to be difficult to make?

Er... No.
Take a look at the Celestron Barlow 2x.
Check out the two, non-functional, external tapers.

Now look closer, at the vertical middle of the lens.
A taper almost meets the
sliding fit cylinder, but stands proud, and presents a shoulder.

image.jpeg.27510f3c24e422b14c0b9d769ff32d6c.jpeg


What if that taper was fully machined to the edge of the top element of the lens?
What if the scope focus tube had a corresponding taper?

What if the ID of the Barlow was chamfered, and each lens?

... They would all automatically locate centrally.

If this taper was a little more shallow ... perhaps in the 5 degree range, it would become sufficiently self locking, without difficulty in breaking the lock.
Potentially removing the need for finger screw clamps ... that require drilling, tapping, and producing a knurl-ended screw.

Why is life like this (you may be asking)?
Or specifically ... why didn't the superior system evolve out of the inferior system, when it could do so without negative impact?

Hmmm ... it's complicated.
Back in the 70's I designed a superior stock control system for a major multi-national engineering company.
It was never implemented ... because it highlighted how crap the current system was, therefore highlighting how crap the factory manager was.
Therefore, the improved system was never put forward for approval.

Ha!
It was one of those early lessons in how life is ... and nothing has changed.
If anything (certainly) we have gone backwards.

Yes, there are other reasons ... incompetence, unwillingness to rock the boat
... or maintaining bad systems, in order to enhance the differentiation between good systems.

Either way...
You can appreciate that my beautifully made lenses, suffer the sliding fit problem.

My electrical tape (in the focus tube) solved the issue with the primary interface.
It's perfect.
The laser can be inserted, rotated, and it stays on point.

Laser-screen-60mm-lens-centred.jpg.570859515d45dbd6d13eda66ad15c2a5.jpg


Insert the Barlow, and it's female interface is too sloppy.
The laser is off point.

Laser-bar-screen-60mm-lens-off-centred.jpg.93355c62ca9e33757ff4e7d5d49faadf.jpg


This means that the lenses inserted into the Barlow will also be off point.

What to do?

The Barlow ID = 31.9mm
Laser & eyepiece OD = 31.6mm

Hahaha ... the laser and eyepieces, rattle around in the cavernous Barlow aperture 😁

The correct solution is to reduce the Barlow ID.

I could increase the OD of the other components, but that would mean for every lens in the future.
No.
The way forward, is to add material to the internal face of the Barlow cylinder.

I'm going to investigate this ... but what a waste of time.
I don't mind messing around with sewage, and automotive components, to get them to fit
... but messing around with lenses is sad.

Now, if only I had a lathe....  🌝

Edited by Fo_Cuss
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Being a manufacturing/ production engineer for fifty years, I appreciate your frustrations.....

BUT you're currently playing with, I think we agree, a scope from the bottom end of the market.

There are thousands of amateurs using refractors/ reflectors which although not perfect are capable of performing to their needs.

I do have one serious area of "complaint" - the "safety recess" found on eyepieces/ accessories was invented by the Devil - and should be banned.

Ken

 

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Ken, I know, that you know, that I know that 😀

My point was not relating to peoples perception of need; as that changes with education.
For the most part; belief in what is, is no different to 'ignorance is bliss'.
(Buy the lens, pop it in ... it's great)  👍

My main point, was that the humble taper, in a production context, provides a low cost solution for 'low end scopes'.

One off, on a lathe, it is much more complex to produce ... but not for a production engineer ... it's simply a taper rather than a shoulder.
(and in this context, only the angle is important ... not the depth ... so easy peasy)

Also Ken, surely I am worth forgiving?
It was a rant, based upon the truth of the situation.

In my book ... these truths are worth spreading, because everything is being dumbed down
... even engineering education
(and I know, because I have a son that is going through it)  🙁

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Increasing The Barlow ID

I need to make up 0.3mm
This means adding 0.15mm to the sidewalls.

Paint
A two part liquid epoxy offered a potential solution, but I was concerned with getting an even thickness.
Instead, I decided, rightly or wrongly, to proceed with spray paint.

The top of the Barlow unscrews ... it is just a hollow shell.
A tapered grinding tool fitted the threaded end ... very convenient with an attached shaft, for inserting into a hand held drill.

The grinding tool was taped to the top element of the Barlow
... and the assembly was placed in the drill chuck.

Primer
0.15mm is quite a gap to fill, and anyway a good key is required.
Hence, I decided to lay down a primer base - typical automotive paint.

After experimenting ... the best method is to trigger the drill slowly, and in very short bursts, spray centrally into the Barlow shell.

There is no throughput, so it is the worst spraying scenario possible.
However, by spraying into the middle of the cylinder, the air/paint jet fans out to the sides, and then returns up the sides of the cylinder, and out (towards you).

Here's what the setup looks like, after two coats of primer.
 😢 my lovely Barlow Lens 😢

Barlow-ID-spray-01.jpg.69ab5eb34346da02e0b5a56f8c0326f8.jpg


I'll probably apply around 6 coats; leave it to dry, and then bake it, before measuring.
(I will clean it up before baking)

My intention is to apply a layer of barbeque paint, and then lacquer ... which can be baked to a hard finish.
Hopefully capable of withstanding the insertion of eyepieces 🙏

 

Edited by Fo_Cuss
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Increasing The Barlow ID - Base & Clear Coat

Having left the primered Barlow cylinder curing overnight
... it was externally cleaned with acetone dampened cloth.
(thankfully the acetone did not damage the lens lettering)

The piece was then baked for 10 minutes at 80°C then 30 minutes at 180°C

After cooling, the surface was rubbed with a fine abrasive paper
... this to enable a mechanical bond with the base coat.

A superior mount to the drill, was made, using a nut and bolt and some large washers.
A larger nut was used within the large washer, to keep the bolt close to the centre, in order to make finding concentricity easier.

The matt black was then applied - 3 coats - each coat blasted with a hair dryer for a minute or so, before the next coat.
This seemed to be fine.

Barlow-ID-spray-03-Tape-Mount.jpg.6bf3873bf66cc1fe1a8fa3d8a79b5a0a.jpg

Barlow-ID-spray-02-Black.jpg.fc6866cc23f4f73b7a8bbc5c66efee80.jpg

The clear coat was applied directly after the final black coat had been dried for a minute (till it had turned matt).

The same procedure of spraying and drying was used, in order to rapidly build a layer of lacquer, without runs.
Again, this seemed to work.

Baking - the temperature was set to 180°C
This was a mistake.
The solvents bubbled out.

Barlow-ID-spray-04-Lacquer-Fail.jpg.6d009cca93a2bfcfd116e7abeca0e5d9.jpg


The initial removal of the solvents should have taken place at a much lower temperature
... perhaps slowly bringing the temperature up to 50° and leaving it there for 15 minutes, then another 15 minutes at 80°
... before hitting the baking temperature of 160°C (rather than 180°).

Or, just warm it with a hairdryer, and leave it overnight (as done with the primer), before baking.

I was basing my information on car spray curing, however, the car industry likely use '2 part' lacquer.
The lacquer that I was using was normal spray can type, and full of solvents.

Never mind ... it is a learning process.
For those wishing to enhance their Barlow lens, these mistakes can be avoided.

The good news is...
The eyepiece no longer fits.
So the process can build the required thickness.

The slightly overcured lacquer can now be rubbed down.

I will likely use a half-round file (or something similar), to support the abrasive paper.
Rotating the piece in the drill, should then enable rapid polishing.

A hole will need drilling in each removable eyepiece cylinder, to allow the air to escape, when fitting the eyepiece in the Barlow.
If this wasn't done, the eyepiece would become a compression piston.

These are the next tasks.... 🌝

 

Edited by Fo_Cuss
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Increasing The Barlow ID - Finished pre-tidying

This mod was a nightmare!
It has succeeded; but it is not ideal, AND it needs tidying.

The task will always carry difficulty ... but, with a better method, it could have been easier.

Introducing The Method

The Barlow lens cylinder (separable from it's lens), which holds the eyepiece ... is too large in diameter.
To reduce the diameter ... material must be added to the internal surface.

The difficulty, is in adding the material uniformly, in a manner that is readily available.

Spray paint, is readily available.
However, spray paint is difficult to apply in a small diameter cylinder...

The Method

Mount
The first, and most critical task, is to create a mount, that can rotate the cylinder perfectly concentric, in a drill.
If the cylinder does not rotate perfectly central to it's axis ... the applied spray paint, will 'puddle' to one side, to balance the centrifugal force.
IE. The paint layer will not be evenly spread.

All time necessary, should be taken, to achieve a perfect spinning cylinder, in the drill.
If this is achieved, the task will be 'one hundred fold' easier.

The paint layers can be sprayed, and centrifugal force will spread the paint evenly.
Note: Lighter coats are less problematic.

Masking
Tape will need to be applied, and removed before each bake.

Use a scalpel, or sharp knife, to make an opening for the clamp screw.
This to prevent the threads from being filled.

Primer
Two coats is sufficient.
Even when baked hard, the primer is much softer than lacquer.

It can be heated between coats, with a hair dryer, and left overnight, before baking.
It may be possible to speed the process, by warming the piece to 50°C for 15 minutes, and 80°C for a further 15 minutes
... then baking for 30 minutes at 180°C

Base Coat
Typically a matt black - these are extremely thin coats.
Three coats will be likely sufficient.

In the automotive industry, the base coat is cured with the clear coat.
However, in this instance, with the matt finish presenting an excellent surface for clear coat bonding
... The base coat can be baked.
Due to it's thinness, ten minutes at 50° & 80° should be sufficient, before baking at 180°C for 30 minutes.

Clear Coat
Apply two coats, and bake.
Either leave overnight first, or gradually burn off the solvent, as per the primer.
Baking at 160°C for 30 minutes, should be sufficient.

Measure
Offer the eyepiece to the Barlow cylinder, and decide if another lacquer coat is required.
Depending upon the play ... but in principal ... proceed with one additional coat at a time, as lacquer goes on thick.

Finishing
If the final coat was just too much...
Use abrasive paper, supported by a pencil or half-round file, to reduce the diameter.

If the mount was concentric, this surface cleaning should be straightforward.

Final Considerations
This task should not be undertaken lightly, and not rushed.
Having said that ... the goal of self-centering lenses can be achieved.
Thus, improving the focus, and image sharpness, when using a Barlow lens.
... to what degree of improvement, is not clear at this moment.

What we do know is that, with a sloppy eyepiece inteface, the test laser beam was nowhere near central.

How did it go for me?

Bloody terrible 🙁😁

The die was cast, when the first mount was not concentric.
This produced an oval diameter from one side.
However, it is not possible to know which side, until the primer is revealed, when using emery cloth.

Oh ... it was the other side 😀

Also, I had applied too many coats of primer, compared to lacquer.
Ha!
The project was falling apart, and all that I could do was go with the flow 😉

The saving grace, was that : deeper into the cylinder, the paint had gone on more evenly
(this is what 'phew' means)

After hand relieving high spots, and uncovering vast swathes of primer...
I was able to rotate the piece in the drill again, and (with repeated testing), ease the eyepiece into the Barlow cylinder
... until it was finally a snug fit.

No need for drilling the eyepieces ... the air can escape, if the eyepiece is steadily inserted.

I know that I can add a thin coat of matt black, to make the Barlow look nice again (and clean up the outside edge face).
However, I figured that it would be best if you saw the Barlow cylinder 'warts and all', prior to tidying.

Barlow-ID-after-spray-Rough-06.jpg.043c2c1811ccc033b8b492773a64cbac.jpg


With the outer edge face, taken back to aluminium, and a thin coat of matt black, to cover the primer
... nobody would know the grief that this has caused me 😁

I reassembled the Barlow lens, and checked it with the laser.

I found that there is a position (Celestron text to the top) where the laser seats perfectly (or as near as damn it).
Good enough; and far better than it was.

Here's how it tested:

Barlow-ID-laser-centre-after-spray-05.jpg.357a22bc09b92842ce1153204697856d.jpg

The above test saw the laser being used on position 4.
In the Barlow, this produces the circle of light that you see.

You can just make out the centre hole ... the optical effect rings are fairly concenric to that hole.

I believe that the setup can be improved, by carefully rebuilding the lenses (they were rush assembled).
However, the main point is that the Barlow can now be used with confidence.

What a job!
Thank goodness it is over (or almost).

I'll tidy it up, reassemble the doublet objective lens
... and then try and grab some benchmark images for the 60/f700 scope, and the various eyepieces.

Just need clear skies now 🌝

 

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Increasing The Barlow ID - Examination

The surface was given another coat of matt black.
This proved to be very useful.

The eyepiece would no longer enter fully, and all the contact areas (surface to eyepiece) gleamed.
Using a wide-angle lens, these markings were captured.

First note the shiny ring towards the bottom of the cylinder.
... visible evidence that the paint, at the bottom, had centrifuged evenly.

Not all the rubbed areas have shown up on the image, but some solid black regions can be seen:

Barlow-ID-rub-marks-07.jpg.d3e3105388a7775378e8eaffe550cf99.jpg


I have decided to spray some paint into a small container, and attempt to build the low areas by hand.
The entire surface doesn't need to rub, but a little more support is preferable.

This got me thinking...
Perhaps the centrifuge can be done away with.

A thin sponge pad, glued to something like an iced lolly stick, carrying a small quantity of paint, evenly spread over the sponge
... the paint could be easily wiped around the surface.

A drill mount would still be required, for the abrasive work, however perfect concentricity to the drill is less relevant to this task
... the abrasive would only see a rotating cylinder.

Hahaha ... the method continues to evolve.
If I was doing this again, I guess that I would apply the coating layers by hand.

... but that is just a guess, for the moment.
I'll have a better idea, after I have tried the detailed 'filling'....  🌝

 

 

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Increasing The Barlow ID - Fine Tuning

Cutting to the quick ... the paint brush 'filling' worked.

I first planned how to do it - holding the cylinder to a light
... and located a small, fine, artists paint brush - which was trimmed with scissors.
Paint was sprayed into a small, flatish, glass candle well.

The paint appeared to be slightly thick, and probably could have done with one, or two drops of acetone (no more).
However, I figured that I should 'go for it', as there was only one way to find out.

The paint was quickly applied to the low points ... it was getting thicker by the second.
The last application was 'the last application'.
For other uses, it was still usable, but it was getting thicker as the solvents evaporated.

It went in the oven to 95° and ten minutes later, to 160° for around twenty minutes.

It bit me!

Wanting to get on, I grabbed it with a beer cloth (instead of leaving it to cool down).
It was good that I did; because I discovered that the paint was in fact soft when hot ... it hadn't cured.
Inadvertently, I had caught some of the paint with the cloth, and it had simply rubbed off.

Well ... you learn something every day.
I've sprayed a large number of items over the years, and always assumed that baking would leave the paint hard (even at high temp).
Maybe it does, with other paint, but this was a high temp BBQ paint - clearly designed to withstand far higher temperatures than the primer.

Yes ... another lesson learned!

No matter; I let it cool (and then it hardened up).
Allowing me to give it a slight cut with fine carborundum paper ... just to remover the matt peaks.
(I cut a 10mm wide strip from a leather belt, to evenly support the paper)

I also took a few microns of paint from the lower area where the eyepiece struggled to enter.

Yes ... I could immediately feel that the extra support had improved the action of inserting the eyepiece.
... it rode home, on a cushion of air.

There was still some sticking.
The hot-spots were taken down individually, and a few more microns removed from lower down.

I finished it off with talcum powder, and the 12mm eyepiece.
This did it ... probably 1 micron; and after cleaning off, all the eyepieces enter on a cushion of air.
Effectively, the limit before an 'interference fit' 😎

No photos ... you need to see it on a video (when I produce it), showing the eyepieces sliding home.

It wasn't over
The laser was not fully penetrating.
It does not have a fine machined finish, and it had a paint finish that was slightly mottled.

I took 1000 grit paper; and with the leather support, I cut a 10mm band, removing the paint peaks.
... and the sharp end edge was removed.

That was it.
The full kit could enter the Barlow, without a hint of play.
The 'sliding fit' assembly method, had finally been taken to its ultimate conclusion  👍

Laser Test

It works.
I took it out, and reinserted it a few times, to establish confidence.

I tried to gently force it off centre.
This can be done.
Not by much, but it can be done,

However, by following a procedure; letting the components find their way; the centre can be maintained.

What hope, a normal setup has?
None!

All that effort ... was it worth it?
I would say 100% yes.

The standard Barlow was miles out, over 700mm.
At 1000mm, the laser point would likely not even hit the lens.

Could this be why astronomers complain about the drop in image quality (when using a Barlow)?
I do understand the mod it makes to the focal length, but perhaps this is only half the tale.

Shame that I do not have any benchmark images for the Barlow (pre-mod).
Anyway, we will see what we see.
I have a Plossl 6.3, and an Omni Plossl 12.
The 2x 12 v 6.3 will have to do, to determine the viability of the Barlow.

Next up, we will reflect upon what we have learned.
I know that this has been a continual process (as it should be)
... but it's only when a project has been completed, that the lessons are fully appreciated, and taken en board 😉

🌝

 

 

 

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Increasing The Barlow ID - Reflections

There have been two trains of thought:

  • The concept
  • The method - how to better repeat this task

The Concept
In principal, a lens system will produce better images, if each of the lenses is aligned.
An eyepiece lens, might have a number of component lenses ... each perfectly aligned.
That is, until a Barlow lens is added to the eyepiece.

By reducing the sliding fit between the eyepiece(s) to almost zero, the Barlow can become 'one' with the eyepiece lens system
... enabling laser collimation with the objective lens, to create a single lens system.

In fact, if using an erecting prism, it doesn't end there.
However, the concept is clear, and valid.

The Method
The ideal method has not been proven.

However it is done; material must be evenly added to the internal diameter of the Barlow cylinder.
If the surface has already been painted, I would forgo primer and base coat, and directly apply lacquer
... it goes on quite thick, and can be easily baked hard.

Applying thin layers with a fine artists paint brush, is likely to be less problematic to using centrifugal force.
The key will be to apply  just enough to cover the surface without runs.
Finish by dragging the brush outwards towards you, so that the lacquer grain is perpendicular to the circumference.
This will enable easy and controlled removal of the peaks.

A mounting bracket to a drill, will be required, involving a screw, nut, and various washers.

200, 500, 1000 grit paper should be sufficient.
Cut a 10mm strip of belt leather, to support the rubbing paper.
This will be strong enough to apply pressure over the length of the cylinder, whilst forming well to the shape.

Having a very small, kitchen work top oven, will be ideal for baking the laquer finish - from a time and cost perspective.
Raise the temperature in stages, to first eveporate off the solvents, before taking the temperature to 160°C  for 30 minutes.
Let the piece cool to room temperature, before working the lacquer.

Whatever happens, you will succeed.
The only question is, how long it takes?
In my estimation, the above method will prove to be much quicker than all the steps that I was forced to take.

Once completed, the lower portion of the cylinder (beneath the penetration point of the eyepiece) can be blacked.

🌝

 

 

 

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Preparation for Benchmark Testing

90° Erecting Prism
The entry to the focus tube, and the aperture for eyepieces ... both were sloppy.

The male entry tube - I first tried electrical tape, but it was too much.
I resorted to aluminium tape.
It's not ideal, due to it being soft, and has potential to tear
... but it fitted perfectly, so good enough for the time being.

The female eyepiece connector was sloppy, and of course, the prism is akin to bingo balls in a lottery.
(The first 'light entry' error, is doubled at the first bounce)

Within the play ... at 90° angle, the eyepiece (and camera) tilt backwards.
The light could be going anywhere.

I tested with the laser; hoping for a lucky break
... and got it!

Yes; all that slop allowed the centres to align; or at least come very close
... the laser point was (horizontally) only 3mm off
... vertically, it was cock on.

Probably, a small piece of electrical tape will be enough to achieve guidance
... but as it stands, it's not too shabby :)

Camera Mount
The camera is an LG4 mobile phone.

Using a spare skin, I had hot glued a plastic cylinder, cut from an aerosol spray can top
... this for the original kellner type lenses.

The annoying problem was that the OD of the Omni Plossl's was larger
... so the first mod had to come off, and I needed to find a 34mm ID replacement tube.

The top of a water softener bottle was almost dimensionally correct, but it needed the support of a sink drainage tube.
When cut to size, the two together, glued to the phone skin; provide a perfect interface for connecting to the telescope.
It is definitely not pretty; rather it is function over form.
... but if a press fit connection for a camera is required ... this is as good as it gets (and far and away superior to the available mobile phone mounts).

LG4_skin_connect_Omni_eyepieces.jpg.1e65244ac8cf88bd4bcbfbfd87896146.jpg


The eyepiece is pressed into the connector, and the assembly is mounted to the scope.
No messing around - it is perfect alignment every time.

Next to the phone skin, is the 'tape modded' prism.

Benchmark Planning

Including the original kellner type eyepieces
... grab images for the eyepiece range (at 10Km).
Repeat with prism.
Repeat with Barlow.
Repeat with Barlow & prism.

Grab an image straight down the scope (sans eyepiece).

Obviously it is a shame that we don't have a full range of shots from the scope, precollimation & firming up.
Never mind ... I do have a couple of shots to compare with.

Primarily, this will benchmark the 60/f700 setup.
It will allow us to judge the 90/f1000 effectively, and the eyepiece improvement over the original kellner type lenses  🌝

Edited by Fo_Cuss
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Benchmark Testing - The Event

Last_Minute.com

Benchmarking is no different to going camping.
Ideally, all material preparations should be completed, the day before the event.

This was to be completed today, with a view to testing tomorrow.
Only that today turned out to be a very nice day, with visibility calculated at 40Km
... while tomorrow indicates rain.

Knowing this, the Pixies got to work, applying particles to the Kellner lenses; forcing each to be cleaned.
The test schedule was not printed on windproof card ... and not even on paper.
The camping table needed setting up and cleaning - so it stayed at home.

Really; having a table, with all the lenses laid out in known positions, would be the way to do it
... particulary with the number of tests required.

Instead, the lenses in their cases were placed in container, which was placed in a rigidish supermarket shopping bag.
It was fine enough, but a touch messy.

Overall, it would have been better to have got the testing underway an hour earlier
... but it could have been much worse.
The sky was mostly clear, and the winter sun was low in the sky, at 14:30hr when the first image was taken.

The Testing

I quickly discovered that the scope needed to be in the shade (to enable 'image viewing').
Thankfully, the Berlingo is tall enough for the winter sun.

Initially, there was no wind, though it arrived soon enough.
Ha!
For all the 'damping work' done ... it must still be improved.
Either that, or a Bridlington type wind-breaker must be constructed (I think I have one somewhere).
... actually, a tall top-sheet tent  would be great

Focussing was okay at low maginfications ... 4mm was difficult ... 2mm was virtually impossible.
In fact, focussing with the Barlow was generally more difficult, due to the extra weight and length.
(I'm thinking about a gas strut, say, from a hatchback door)

But the Barlow testing was carried out when wind gusts were more prevelant, so it was a double whammy against me.

The 'camera mount tube' needs to be longer, to provide better support for the weight of the phone
... the eyepiece had to be too close to the camera lens.
(Thankfully, the hot glue system allows for easy mods, simply by using a hair-dryer on it)

Recording the results

The main bugbear is the inability to easily record which image was taken by which lens setup
... and it's not like there was just one image per lens.
I was using a 'hand clap', but add in some wind rafals and the damned camera is snapping away happily on its own 😀

What I did, was to switch to video between major changes, to verbally record what I was testing.
If I hadn't done this, the results would be meaningless.
Having said that ... the images now need to be sorted, so we will see how rigorous I was with my book keeping.

Overall, as with the preparation (of course the two are linked), the benchmarking could have been better
... but it could have been much worse.

It definitely needs a table, with the lenses laid out in order, a card printed schedule, and a pen, to note the exact time against each lens change.

If all is well organised; one man can do it.
However, a two man team would be ideal - one on the table and record keeping, the other on the telescope.

It wasn't to be.
Though, the testing wasn't by any means, a disaster.
Hahaha ... well ... I guess that we are about to find out  🌝
 

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Benchmark Testing - The Results

What is a Benchmark?
This is a record of a current setup, prior to implementing modifications
... in order to be able to gauge the degree of improvement, or lack of improvement.

Consequently, it is an education aide, as one can precisely reference what hes been done well, and not so well.
Similarly, it is used for material and component comparison.

Why not just see if the new kit is better?
For simple comparisons, this is possible - I got a new pencil, and this one doesn't break all the time!
But in complex scenarios; sense and feeling is often based on how you got out of bed that morning  😀
Also, if a large sum of money has been spent on new kit, you may tend to believe that it's better, when it may be no different  😉

Can results be valid in a complex atmosphere?
Validity of results is always open to question, outside of controlled laboratory testing.
The best that can be done, is to take a record of atmospheric, and sunlight conditions.

There may also be a questionmark over the improving skills of the tester, between benchmark tests
... Er ... That applies to me, because I have very little prior experience with telescopes and telescope imaging.

Consequently; a set of benchmark results can masquerade as precision data, when it is no such thing.
This caution certainly applies to the benchmark results below - the difficulty in focussing, wind, and camera settings  :eek:

However, these factors are referenced.
... and from this, we can view the results as being a benchmark for a starter scope.
IE. This is what you might expect, with a 60/f700 with these lenses.

When all that has been learned is input into the next version 90/f1000 ... we will see the improvement.
Hence, in this context, the results below are valid.

Tests
Wind turbines at 10Km

  1. Through the 90° prism
  2. Through the focus tube
  3. Through the focus tube and Barlow 2x

All the images were taken at JPG 90%
145 images were taken in total

Note:
Having analysed the images, I discovered that the camera should be set to close-up, not infinity.
The difference is in, more or less, ghosting.
Annoyingly, other than the first images, the setting used is not known.
(the opening images are presented to show the difference)

Note:
The Kellner lenses are starter eyepieces (came with the scope)
The Omni Plossl range were in fully marked up Celestron packaging.
The 6.3 Plossl (marked as Celestron) was gifted in a white box.
(I say this because the 6.3 results appear to be sub-par)

Results Format

For each test completed, the best image was chosen.

The post processing was limited to :

  • Rotate where necessary
  • Crop to 946 x 946
  • Crop and RESIZE up to 946 x 946 where necessay to compare specific object image reproduction
    ... relates to comparing high magification or camera zoomed images (big to start with), to what a low magnification image provides when zoomed in Gimp (interesting)
  • Processed images were saved at JPG 100%

Weather for the test period :

Benchmark_01_Weather_(cut)_2019-12-07.png.55fc7308a8041211f5454c162158912b.png
 

RESULTS - By Prism

Prism_20_Kellner_Infinity . . . . . . Prism_20_Kellner_CloseUp
Infinity and closeUp refers to the camera focus setting.
Actual scope focus probably changed between each shot.

Prism_20_Kellner_Infinity_RESIZE_20191207_143821.jpg.84ec7e4e0ffd64b68906416d678932c4.jpgPrism_20_Kellner_CloseUp_RESIZE_20191207_143852.jpg.5e72f1ec5370483e6b1b9255edb9ffc3.jpg


Prism_12.5_Kellner_CUT . . . . . . Prism_9_Kellner_CUT

Prism_12.5_Kellner_Infinity_CUT_20191207_144415.jpg.895c57045730b9ccc02b8ee4099c8160.jpgPrism_9_Kellner_CUT_20191207_144746.jpg.f0cd0fccd2f0a3ad622a613f3ceb01dd.jpg


Prism_4_Kellner_CUT . . . . . . Prism_6.3_Plossl_CUT

Prism_4_Kellner_CUT_20191207_145201.jpg.a2998109531e0a4e8324ff459a525ce6.jpgPrism_6.3_Plossl_CUT_20191207_145438.jpg.8e60e7fb560563a7e0c196950213c5d0.jpg


Prism_12_OmniPlossl_CUT_RESIZE . . . . . . Prism_12_OmniPlossl_CUT
Prism_12_OmniPlossl_CAMZoom_CUT . . . . . . Prism_4_OmniPlossl_CUT

CAMZoom was a different image, hence a resized cut of the first image was produced
... to indicate whether camera zoom should be used (or at least the difference)
Just to be clear: The top two images are exactly the same.

Prism_12_OmniPlossl_CUT_RESIZE_20191207_150033.jpg.ab57342bb3d911fd5a0288aeafcc8af1.jpgPrism_12_OmniPlossl_CUT_20191207_150033.jpg.ed8f3a19f936b9e0adeeefaf21f7f51b.jpg

Prism_12_OmniPlossl_CAMZoom_CUT_20191207_150017.jpg.675f60ff8e3452f1cfc368985eec9c0b.jpgPrism_4_OmniPlossl_CUT_20191207_150205.jpg.aa9d24d34be498a3ea929e321b9c004b.jpg


RESULTS - By Focus Tube (direct)

Direct_12.5_Kellner_CUT . . . . . . Direct_12_OmniPlossl_CUT

Direct_12.5_Kellner_CUT_20191207_151234.jpg.d6774ab93f21c4feca6a9582cf34439c.jpgDirect_12_OmniPlossl_CUT_20191207_152338.jpg.c5f5daf2914bd3e55bf16d0877c042e8.jpg


Direct_4_OmniPlossl_CUT_RESIZE . . . . . . Direct_4_OmniPlossl_CUT
Direct_4_OmniPlossl_CAM_ZOOM_CUT
. . . . . . Direct_12_OmniPlossl_CUT_RESIZE
These somehow bypassed the rotation phase  :icon_albino:
... and yes ... the top two images are the same!
The 12 RESIZE is from Direct_12_OmniPlossl_CUT (above) - would you believe it  :smiley:

Direct_4_OmniPlossl_CUT_RESIZE_20191207_152723.jpg.9f3aa23ef0bf2a64d0ac7b488cabd0e0.jpgDirect_4_OmniPlossl_CUT_20191207_152723.jpg.951fdcc66c1473f5b48fa47916453ff8.jpg

Direct_4_OmniPlossl_CAM_ZOOM_CUT_20191207_153256.jpg.684b8fd894a1bd60d50785fa398758ff.jpgDirect_12_OmniPlossl_CUT_RESIZE_20191207_152338.jpg.8d7d8228c9d5cef4182bd0855ebbc3df.jpg


Direct_6.3_Plossl_CAM_ZOOM_CUT . . . . . . Direct_4_Kellner_CUT
For Direct 6.3 Plossl only a camera zoomed shot was worth posting
... the Direct 4 Kellner compares quite well.

Direct_6.3_Plossl_CAM_ZOOM_CUT_20191207_153713.jpg.efb00ed77ce01e64ee8ee9d2959d7587.jpgDirect_4_Kellner_CUT_20191207_151836.jpg.868a5c43d9666ab0a9d92c39b5597eeb.jpg


RESULTS - By Focus Tube & Barlow

Barlow_12_OmniPlossl_CAM_ZOOM_CUT (6mm) . . . . . . Barlow_4_OmniPlossl_CUT (2mm)
Barlow_6.3_Plossl_CUT (3.15mm)
For the Barlow 4 (2mm) - walk 3 paces from the screen, and look (the image is there).

Barlow_12_OmniPlossl_CAM_ZOOM_CUT_20191207_154529.jpg.fdda6a7cc8de60a3ed45f9bb71e9b5fb.jpgBarlow_4_OmniPlossl_CUT_20191207_155949.jpg.360693b265dc906327dfffe7be1535d2.jpg

Barlow_6.3_Plossl_CUT_20191207_155110.jpg.13b9623690ecc16d5edae44231060201.jpg


Conclusions

At this stage, with this first benchmark set of results
... due to all the reasons stated in the preamble, we can only judge the results, and not the kit.

Was the 6.3 Plossl doing a 'Hulkenburg' ... basically good, but didn't pull off a good shot?
I have my doubts.
It seemed to perform worse than the starter Kellner 4 (which I thought shone, considering its lowly status).

We can place our bets on eyepiece performance in the upgraded scope.
However, having contacted BET Free Six Five ... there is no money to be earned on the 4mm & 12mm Omni Plossl's
... both of which put in a very good performance (regardless of the crappy choice of camera focus).

Interestingly, there is a good gamble on the Barlow.
It showed a hint of promise, when mated to the 12 Omni Prossl.
The thing is; it was last out, the wind was up, the light was starting to go.
It might be worth a fiver on it ... or am I just being hopeful, after burning so much wax?
Genuinely ... I don't know
... and that's exciting.
Will it, or won't it come good, in the 90/f1000 hyper scope ?  😎

The Winning Image

Ha!
This is the strange thing about pictorial elegance.
The brain just likes a good photo, even if it might not have the best data
... zoom in, and you could have a good argument.

But there's no doubt that the Direct_12_OmniPlossl_CUT appears to have that confident 'look at me' stance
... and eye's are drawn to it.

The Omni Plossl 4 has a lot to say about this, but is wisely keeping its powder dry for the next showing  😉

So let's leave the 60/f700 Benchmark Tests, with the 'Direct_12_OmniPlossl_CUT' on display :

Wind Turbines at 10Km (Celestron Omni Plossl 12mm - Direct through the scope)

Direct_12_OmniPlossl_CUT_20191207_152338.jpg.c5f5daf2914bd3e55bf16d0877c042e8.jpg


🌝

 

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  • 2 weeks later...

Modding the 4mm Omni Plossl - Part 1 - Introduction

It exhibited problems.
Perhaps much is due to the scope requiring flocking ... but even still...

If we examine the image - the eyepiece aperture is ringed ...
An external glare is clearly visible; and so too an internal band, that starts black, but then changes to white(ish).

Edge-Problem_Direct_4_OmniPlossl_IMG_20191207_152629.jpg.51b593d142b36711a5e200b344600ad9.jpg


The External glare can be highlighted in Gimp :

Edge-Problem_Direct_4_OmniPlossl_OuterGlare_IMG_20191207_152629.jpg.729b3dab9fee7c018a43fb03945da414.jpg


So too the internal issues :

Edge-Problem_Direct_4_OmniPlossl_InnerGlare_IMG_20191207_152629.jpg.7d67afcc545e3758fb6816189ab481af.jpg


Ha!
It shows that the camera lens was not quite aligned to the eyepiece; though that is nothing compared to the bizarre banding problems.

Yes ... the whole image contrast would (will) benefit from flocking, but the primary issues relate to the lens, the camera lens, and the bouncing light and shadows.

From the images, there was no escaping the fact that there were issues relating to the aperture edge, and the light bouncing between the camera lens, and the eyepiece face...
That's not mentioning the progressive banding, that could be coming from internal issues within the eyepiece.

Identifying the areas for improvement

The first issue was that the camera lens FOV was greater than the eyepiece aperture, and this was creating a shadow.
Also, the light was bouncing off the camera lens ring, and the eyepiece face.

Within the eyepiece, the locknut was finished in mirror black anodising, with a major chamfer that would bounce light incorrectly into the lens.

What else would be discovered, depended upon dismantling the eyepiece.
... something that had to be done, if the shadowing was to be removed, by executing a chamfer to the eyepiece body aperture.

Opportunities

Dismantling would enable further investigation of internal reflection, lens edge blacking, and lens construction.

... and so, the adventure began....  🌝

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Modding the 4mm Omni Plossl - Part 2 - The Components

Lens Adapter Tube

Nicely machined, with a continuous internal thread, through the length of the adapter.
The threads are black anodised.
This anodising can come off, due to screw friction, though the glare would be hidden by the lens body.

The problem would be when filters are screwed in and out, leaving bare aluminium when filters are not being used.

Otherwise, the taper of the thread causes the light to bounce back into the scope.
When viewed from the other side, there is only a small percentage of reflected light entering the lens.

  Sorry about the quality of the images.
  I moved from 'stills' to 'video', in order to capture the project.
  Of course, one then forgets to take stills.

Here's an image showing the light bouncing back towards the light source (out of focus - damn!)
... and another image, viewed from the other side.

OmniPlossl_tube_light_reflected_back.png.9dc4a1bf1f18185a1e644058839a3010.pngOmniPlossl_tube_light_restricted.png.a1b00530065360eae4adbb777e1698f9.png


Do we want ANY light bouncing around?
Probably not; and then there is the knowledge that ultimately there will be anodising wear.

My solution to this, will be to make up a removable flocking tube.
Problem solved :smiley:

Lens Disassembly

There are two glued pairs of lenses, separated by a matt anodised steel spacer ring.
These are clamped into the body, by a bright (why ???) anodised aluminium slotted nut.

The required screwdriver head, is the largest cheese-head 'bit' that is included with the typical impact driver set (shown further below).
It fits perfectly, requiring a firm twist to break the friction, before it screws out smoothly.

Both lens pairs appear to be the same in design ... (if someone knows different, please say)

To remember the lens orientation ... think of the scene in the film Stalin Is Dead, where the guys 'belly bump' each other

Stalin_is_dead.jpg.bbde2a691a49b684560e6ac739396574.jpg

If you've not seen the film, then seek it out, because it is hilarious.
Anyway, you will now never forget the Omni Plossl lens orientation, because the fat bellies face each other 😁

OmniPlossl_lens_components.jpg.442c60e85443da1b889a17baf53df19e.jpg


Lens Examination

The eye-side lens appeared to be fine, with sufficient edge blacking.
The scope-side lens was found to be less than ideal.
... being misaligned during assembly, and lacking edge blacking.

OmniPlossl_eye_lens.jpg.30686be9900b5e3f90edf1b55621fcc3.jpgOmniPlossl_scope-side_lens.jpg.f024138a3e6fbea7d90d2dc544bef21b.jpg


Error
It hard measures to 0.06 mm (with cockle), and can be physically lifted at 0.07 mm.
My estimate is that the shift is 0.075 mm.

Not ideal.
... and it's such a small lens, that is known to be pushing the limits.

What to do ?

Leave it, for a later job ?
Or stick it in the oven, melt the bond, and realign the lenses correctly ?

Bloody hell; I've got so much to do ... I just didn't need this :clouds2:

Has anybody succesfully completed an ungluing and regluing of a lens pair ?

I'm guessing that the lenses are superglued together.
The question is ... will the bond re-make on cooling?

The method that I'm considering, would be to place the lens, flat(ish) side down, on wood.
Over-cook the lenses, in order that they stay above the bond temperature...
Using plastic pincers, and a piece of card ... clamp to wood, and apply the micrometer anvils (or vice versa - probably less risky).

Then leave it ... hoping that the bond remakes.

I'd be loath to apply liquid superglue, because it is likely to wick through the gap.
I need 'gel superglue'.

Hahaha ... I might have some; only that if I find it, I'd probably be tempted to execute the repair.

It's not that it can't be done.
It's the risk of knocking the lenses, and smearing the faces with melted superglue.

... and it's a two man job, yet it is such a tiny work area ... and the temperature will be rapidly falling, as soon as the anvils make contact.

However, it IS doable, and should be well within my capabilities :glasses1:
... only that it must be done correctly at the first attempt, if a whole range of complcations are to be avoided.

Lens spacer ring

This component appears to be well made.
The production team did an excellent job with the matt anodising.
Here it is, under lights :

OmniPlossl_lens_spacer.png.d64878151537198e31136d105c748006.png


Clamp Nut
Why on earth didn't Celestron get the same team to make the clamp nut?
... because it is the most brilliant shiny black anodising, that I have ever seen  :icon_scratch:

This image doesn't do justice to how shiny this component is....

OmniPlossl_clamp_nut.jpg.57f06df62d588c185d5e104fa46f4e4f.jpg


Note how the chamfer will bounce light directly onto the mirror surface of the the nut cylinder face.
... and there's more...

The clamp nut has a central 5 mm diameter cylinder.
However, at the top of the cylinder (scope-side), there is an intruding lip of 4.5mm diameter.

OmniPlossl_clamp_nut_lip.jpg.0f426109bbe8109ea95ae179d9e7f03f.jpg


I see no reason for this lip, other than to cast a shadow onto the 5 mm diameter cylinder.

Does anyone know of any other reason, for the existence of this lip?

If my suspicions are well founded, this lip can be removed, and the cylinder flocked with Black 3.0
In doing so, this would increase the amount of focussed light entering the eyepiece, by over 10%.

For an eyepiece that is already suffering from lack of light .... 10% increase, would be a significant improvement.
The thing is ... the chamfer brilliance will already be defeating the shadow creating lip (if that is what it is).

My guess is that it is this combination that is causing the banding aberration on the image.

To be honest, if I had a 5.2mm drill, or a 5.3mm broach, I'd expand the cylinder slightly, to make way for the Black 3.0.
... then matt the chamfer surface, to complete the clamp nut upgrade.

Eye-side lens shoulder - chamfer creation (eyepiece body)

This shoulder (that the lens is clamped to) projects around 1 mm from the lens surface.
It is this that is causing the shadow to the camera lens.

It had a minuscule chamfer - principally to remove the sharp edge.
The chamfer needs to be much deeper. to allow free passage of light from the eyepiece lens to the camera.

While. this area of the image may not be the best ... the objective is to eliminate the dark shading at the edge.

The shiny aluminium chamfer will then require blacking ... at the same time the eyepiece face can be matt blacked, as it is a highly reflective anodised surface.

I've already cut a chamfer, and carried out a large amount of experimental work with paints, primers, pigments, and two part epoxy.
I'll leave that for the next post, but here is an image of the chamfer, after it has been roughed with a diamond file.

OmniPlossl_body_chamfer_roughed.jpg.3ce2f1deb84769d0fa9617963544676d.jpg


In the meantime I'll leave you with an image of the kit that I used.

Oh ... and if anyone has any experience with the lens glue situation, and the strange baffle on the lens clamp nut; I'd be interested to hear from you 🌝

OmniPlossl_tool_kit.jpg.913ba2a60d5ee87172fc77fb10d833f8.jpg

 

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Images from the modded Omni Plossl

The clamp nut ring turned out to be the field stop.
Removing it, would increase the FOV, but the increased area would be degraded.
So, that was a job saved :smiley:

Lens glue is UV bond.
It melts in acetone.
UV bond has been ordered.

The lens edges were blacked
... as was the EP body, and clamp nut.

The adapter tube threads were flocked using card.

A hybrid black was created using acrylic primer, cement pigment, and Black 3.0
... this improves the Black 3.0 durability.

With the lens realignment for later, the eyepiece was reassembled.

The camera adapter was firmed up with a reinforcing band ... it's perfect now (well, almost) :icon_razz:
... it was blacked with a permanent marker - not great, but fine enough for the mo.
... the camera ring was also blacked.

I was good to go :smiley:

Weather was bad, so couldn't get a benchmark image
... instead resorting to 'opening the windows'.

The opportunities are limited to a treetop at maybe 1km.
Difficult to image, with the wind.

Post processing was simple 'levels', to correct the overexposure.
(I look forward to trying 'stacking')

Seedballs without stalks

Taken with the unmodded 12mm Omni Plossl; what is interesting is that the seedballs are suspended freely in mid air.
Perhaps their colour did not get focussed
... or the breeze caused them to disappear into the background.

I'm pleased with the image though; particularly at this early stage, on the old objective lens, and an unflocked scope.
Artistically, I love it.
It would make a great dinner place mat :grin:

Seedballs without Stalks - at 1km - 12mm Omni Plossl

12mm_Omni_Plossl_seedballs.jpg.ac0ee2713bb6154383f9699a3980cd6c.jpg


Seedballs with Stalks

Taken with the modded 4mm Omni Plossl; we get to see the stalks in some detail.

The black perimeter band appears large due to the levels lifting it.
However, it is much smaller than previously ... due to the chamfer mod to the EP aperture.
(The chamfer will be increased, when the lens realignment is executed)

Also, the white banding has gone ... presumably as a result of blacking the eyepiece.

I like this image also ... I can't help thinking of a fruit bowl :icon_king:
... There is a large nest behind the seedballs
... and trapped falling leaves

Seedballs with Stalks - at 1km - 4mm Omni Plossl

4mm_Omni_Plossl_seedball_stalks.jpg.83894fd3ff73a9e4df6a794b2d0882f2.jpg


🌝

Edited by Fo_Cuss
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  • 2 weeks later...

Big Update - Lots to talk about...

With Crimbo fast approaching, and my son back for the hols ... a field trip was planned.
There was no chance of completing the big upgrade
... and anyway, I was (and am) still in learning mode.
Consequently, the objective was to continue upgrading the starter scope, and learn what needed to be learn't.

Flocking - Black 3.0

It doesn't provide the required light absorption.

I'm so pleased that I didn't buy the flocking material.
If I had, I would have never tested Black 3.0

It's not that Black 3.0 is bad ... it's an extremely matt black paint.
The problem is that, in a tube, the photons hit like Barnes Wallace's bouncing bomb.
... they skim the surface, rather than being absorbed; and the tube lights up and dazzles.

Having said that ... I watched a video of someone flocking their scope, using a torch to see how the flocking was laying.
All the fibre tips lit up like a Christmas tree.

The big lesson was : Use baffles.
In this way, the photons might bounce, but most of them will collide directly with a black wall (and be absorbed).

Flocking will be used, but in conjunction with baffles, that follow the cone of light (like multiple field stops).

Prior to the field trip, I fitted two baffles.
One masking the focus tube assembly; the other being placed 90 mm up the scope, towards the objective lens.
At 25 mm diameter, it was smaller than the focus tube internal diameter.
It made a big reduction to the reflected light.

Focus_tube_baffle.thumb.jpg.09ed8b305157d16514e053c2366d510a.jpg
 

Tripod
... was completely re-engineered.

Each element was drilled, and computer screws (for add in PCI cards) were used to form new threads.
They are ideal ... not self tappers, not machine screws ... between the two.
With care, and lubrication; in a 2.5mm hole, they will roll a female thread
... which is very strong, allowing decent torque to be applied.

The central tray, that doubles as the rigid coss member (though it was nowhere near rigid).
... was made rigid, with two screws and repair washers for each arm.

Tripod_support_bracket.thumb.jpg.5cecfd674944f80eddc3f59a1ef2005f.jpg


The original top leg clamps were rubbish ... being slotted, it was impossible to clamp the tripod rigid.
Tube spacers were cut, and placed between each slot.
The wing nuts were replaced by large repair washers and nylon lock nuts.
(Note the O ring - to be referenced below)

Tripod_head_spacers_and_O_ring.jpg.fa228a81477f5364207697364b0081e1.jpg


The tripod is now as rigid as any tripod.

Tripod_assembled.jpg.e212a1d4325d7838dae9a8fc68f28f0f.jpg

Azimuth Mount

This was stripped for re-re-engineering 😎

This time I created a stand-alone bearing assembly, to join the mount to the tripod.
The central shaft from the mount is a hollow cylinder, enabling the creation of an internal bearing surface, using an O ring as the central bearing element.
The face indicated by my nail, bears on the O ring (image in tripod section).

The threaded rod pulls the azimuth mount face, down onto the tripod face, and pulls up the bearing assembly onto the O ring, whilst inserting the central O ring into the azimuth mount hollow spindle ... the threaded rod  being adjusted so that it binds into the blind threaded hole in the azimuth mount.

Phew!
If that sounds complicated ... it was.
... but it was well worth the effort, to gain a perfect 'pan' mechanism for the scope ✌️

Azimuth_mount_bearing_assembly.jpg.8934f459bab9de6c8374f5afac8c6d6b.jpg


The outside of the shaft was shimmed using a wafer thin Herring can 'pull lid'.
The lower internal end of the shaft bears on a second O ring
The top face of the tripod, and lower face of the mount, were lapped together using grinding paste.
Ideally a shim is required ... I used a circlip as a temporary shim.

Lapped_bearing_surfaces.thumb.jpg.80dd7675fecde09ed055dcb866f1e8b1.jpg


The mount can now be clamped up tight, whilst it can be turned without any judder, and it stays where you leave it.

Azimuth_to_tripod_assembled.jpg.c4036e3552afa928860d16380df4ec8e.jpg
 

Focus Tube Assembly

Without any PTFE sheet, I turned once again, to electrical tape, to shim-bush the focus tube.
It is now effectively, an interference fit ... there is no play between the focus tube, and the focus tube housing.

The rack teeth were cleaned up.

The assembly was then given the computer screw treatment, when fitting into the scope tube, whilst simultaneousy laser collimating.
... gaining excellent tracking throughout the focus range.

4mm Omni Plossl Rebuild
... didn't happen.

The UV bond arrived ... how did I get through life without it?
Amazing stuff.
It can be applied in the most difficult areas (even using an artists paint brush) and then set, by using the supplied torch.
... the whole package for around €7  :icon_eek:

No time though, to do the doublet rebuild.

The Original 60mm Objective Doublet
... was cleaned up, as were the eyepieces.

Whilst cleaning the 60mm ... when breathing on the lens, I noticed that it's surface was made up of concentric bands.
I reckon that this is not great.

Having said that; on the...

Field Trip
... Terrestrial viewing wasn't too shabby.
We could identify a balcony rail at 11Km - perhaps 50mm in diameter.

Celestial viewing was problematic, as we were drenched in dew, and all the stars were made up of concentric rings.

Polaris ... DK UMa

Polaris_20191229_122435.jpg.9886f9c8ae4ee439b48dc8bd2d722be0.jpg1988127660_DKUMa_20191229_124921.jpg.210d8a54ba0e2829a785b118d64ac256.jpg


Perhaps this is due to the 60mm lens construction, or perhaps the dew.
If anyone has any ideas...?

The azimuth mount, tripod, and focus tube, performed excellently.
The scope could be easily panned, tilted, and nudged ... keeping the moon in the FOV was not at all difficult.
It was very low in the sky at around 22deg.

Moon_IMG_20191229_115806.jpg.fe2c74b3f34aa0a85660e0bb73d7377c.jpg
 

The focussing was dramatically improved ... very little wobble during focussing.
However, it is still not perfectly stable.

Examination, before ordering more bits...

There are a few things that I want to do ... like fitting a degree plate, and a scope 'guide arm/handle'
... but mainly, I want to get rid of the last bit of vibration, when focussing the scope.

What concerns me is that a small amount of wobble on the 60/f700 scope, will be a substantial wobble on the 90/f1000.

Some time has been spent on a gas mount (off a washing machine).
I've eliminated lateral movement, but it is now very stiff ... and the geometry doesn't help.
It might be hard to get it moving.
Anyway, it has been put aside, until the 90/f1000 has been assembled.

I'm going to drill and tap, three 8mm holes around the azimuth mount, and fit 'shaped shoes' to perfectly clamp the mount.

Other than that, I will substantially increase the contact area at the pivot point, and ensure that each face is flat and square.
This will entail fitting stainless steel plates, either side of the felt damping.

More on that, as it happens .... 🌝

 

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Azimuth Mount Mods

One of the difficulties with casting metal, is that the casting relaxes with age.
... and in the case of the U shaped azimuth mount, the legs become splayed out.
IE. The faces are no longer parallel.
We can screw the clamps in, and easily bring the 'U bracket' back to parallel
... but this compression increases the incidence of resonance.

The solution is to grind the faces to parallel:

U_Mount_1st_Sq_Cut.jpg.2922a55e27fb12b992e09cf18dbd7006.jpg


This isn't a particularly easy task, as there are no straight edges available to provide a datum edge.
However, with care, and starting low down the leg (on the support angle); the faces can be ground to parallel.
(I used a diamond plate, with holes to liberate the filings)

Here it is, with both legs completed:

U_Mount_Final_Sq_Cut.jpg.f661a6b28f271ab412a8dc308368c492.jpg
 

This action, gained an additional 0.5mm gap, between the U bracket faces (the support angles are also now parallel).
In total, the gap between the U bracket and the scope, is 4.5mm.

The scope mounts are in plastic.
They are sturdy enough, but their faces are not flat, and contain two screw holes (for fixing to the scope tube).
These mounts can be easily flatted; but this job must wait until the mounts are repositioned, when balancing the 90/f1000.

Ultimately the overall gap between the U bracket faces, and the scope mount faces, will be around 5mm.

I will install felt damping, that will compress to 1mm.
This leaves 3mm to usefully fill.

The objective is to create a rigid bearing face of 45mm diameter.

The plastic scope mount face is already rigid, therefore a 0.4mm thick 'stainless steel skin' will be bonded to the plastic faces.

As can be seen from the images above; the U bracket faces are only around 20mm in diameter.
This is an extremely small surface area to clamp a telescope (3.14 cm²) 

Therefore, a 1mm thick 'stainless steel disc' will be bonded to the U bracket face
... to provide a contact area of 15.90 cm²

With 4 faces in contact with felt, the difference between before and after the mod, will be:
12.56cm²  against  63.60cm²  - 5 times the damping, 5 times the friction.

As importantly, the pivot damping radius increases from 10mm to 22.5mm.

The scope was pivoting around the 20mm D centre ... easily.
It is not going to find it so easy, when it is clamped between 45mm D discs.

Making the discs rigid

The scope side discs are anyway rigid.

1mm thick 304 Stainless steel is quite rigid.
I will probably heat treat it, to make it brittle, and will certainly bond support legs from the U bracket to the outer diameter of the disc.
I will also extend the disc down the legs of the U bracket, to provide additional rigidity to the bracket legs.

The steel has been ordered.

No excuses remain.
The next task will be to build the 90/f1000 tube  🌝

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Power Pack - Tools - USB Cables - Add-on-Goodies

Okay, okay .... I said 'no more excuses'
But....

There comes a time, every now and again, in everyones life ... when the workshop must be sided up.
It brings countless benefits (not least, morale).
Shelves anew, offer bright temptation for the telescope project...
Somewhere to put things out of the way, as differing elements move forward obstinately.

It's a semi-autonomous task.
I say 'semi', because short term assembly decisions need to be made, and materials/products must be purchased for future use ... pushing purchasing into being a short term decision.
... so the brain must multi-task  :icon_eek:

Power Pack

It's a 'big ticket' item, so it had to be right for the job, and sourced from a reputable supplier.
That involved a lot of research, particularly examining the spec list details.

Having read some posts on SGL, I noted some nice home-made boxed PSU's.
I didn't want to go down that route.
I wanted a high powered lithium type battery, that has enough power to start a 1.9 litre diesel (when the battery is cold and weak).
... supply multiple USB outlets
... and a variety of laptop charging outputs, to 19V DC.

There is a vast array of such PSU's; but the deal breaker was 19V DC laptop charging
(I have a laptop targeted for the scope, with this requirement).

Hence, I was ultimately restricted to the 89Ahr model, that I chose to pay at £42.43 delivered.
I could say 'ouch'; but given that it works as stated, it could prove to be a life saver when caught out in sub zero conditions, when the car 'lead acid battery' isn't feeling too spritely 😉

It has a useful torch, a compass for fun, and a variety of power adapters ... all contained in a nifty case :

89Ahr_PSU_01.jpg.c5bf9c2d541ebc2b930468101dd5638c.jpg


I believe that this PSU is more than enough powerful, to feed two smartphones, a laptop, and a heater element ... for 18 hrs
... assuming that all devices were fully charged, and the heater is only deployed when needed.

Given that it meets spec, it will be 43 quid well spent.

Of course, I had to buy a few USB cables - one with a switch, which I thought to be quite handy at a quid.

Other Purchased Stuff

4 off centre bubble spirit levels, of which 3 will be used.
Inclinometer, to aid object acquisition.
Protracter guage, for similar purpose.
Make-up brushes, for lens dusting.
2 off Thrust bearings, for the scope 'tilt clamp axis'.
3 off thumb screw clamps for the pivot spindle.
2 off extended replacement thumb screw clamps for the scope (tilt clamp axis)
More stainless steel shim sheet - 0.1, 0.2mm.
Steel sheet 'Nibbler'.
Curved scissors.
PTFE sheet at 0.5, 1mm.

... the latter, being then in stock, if the focus tube bush shims give problems.
(Actually, I can't see it. I used highest quality electrical insulating tape as shim material ... it's unlikely that I can better this ... particularly the adhesive :icon_eek: )

This 'scope building' is becoming expensive.
... and there is more to come ... the heater, flocking, felt, and surely other stuff.

It is what it is.
The objective is 'a perfect scope', that doesn't vibrate when focussing (within the bounds of what the lenses can provide).
I'll tot it up at the end, but I'm guessing that it will be heading towards €250.

Assembly Decisions - 60 to 100mm Adapter

I've settled on 3 equidistant pairs of screws
... threaded through the adapter, pressing on the 60mm original tube.

It will be like setting up a giant finder scope 😀

Each pair of screws will enable axial alignment.
The front and rear of each pair, will ensure angular accuracy.

What then?

I'm not sure.

The first objective will be to ensure that perfect collimation can be achieved.
Ultimately thereafter, I will probably shim the gap (adapter to scope tube), and clamp screw, with 6 pairs in hexagonal formation.
(then fill).

Assuming that collimation can be achieved, we will be pretty much home and dry, vis a vis the unknowns.
Still lots of work remaining, but just work (he said, confidently) 😎

🌝

 

 

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More Purchasing... and good moves...

I was watching a YT vid the other night (a sequence of his vids).
A stargazer with a shed load of kit - remotely controlled reflector, and a complex star alignment software package.
... but he was working in his kitchen.

I understand that 'needs must' but...
With the amount of time and financial investment, that this chap has made...
It is clear that no investment had gone into creating a working environment, to deal with the engineering side of his hobby.

It's not that work cannot be completed on a dining table...
The fundamental problem lies with the 'shared area' aspect.

To solve an engineering problem, very often requires that the problem is first absorbed, passed into the sub-conscious, analysed autonomously ... and solved some time later (toilet & seat scenario, the next day).

In a world where one might easily have a dremell type grinder lying around ... being pressed to vacate a work area, can result in catastrophic consequences.

Hand grinders like to walk and jump.
They are like Border Terriers ... they do what they want to do, whilst occasionaly doing what you want them to do.
... and he wanted to grind his Corrector Lens :icon_eek:

Sleeping on this ... you would have a triple layer of plastic masking tape over the lens.
But....

As President Clinton famously remarked during his election campaign - "It's the work area - stupid" (or almost that) 😁

If you want to spend 22 minutes of your life watching a collimation fail; it's here:

https://www.youtube.com/watch?v=WQyMk914nfM

In such a situation; my advice would be to purchase a fold-away wallpaper pasting table, and sequester an area for the duration.
Or; better still...
Grab an area, and plant your flag.
Layered clothing, and a sensible diet, solves most heating issues
... and infra-red ceramic heaters will do the rest 😉

... and if you get an urge to use a tool on a "can't fail" piece of kit ... you should first train yourself to use it.

For myself...

I'm recreating my workspace; in preparation for the scope build.
This seemingly is a digression, but it's not.

It's  a fairly slow process ... life gets in the way.
However, on a neccessary shopping trip, I took a punt on Lidl having a 'bits & pieces' tray/drawer wall unit.
Bingo!
I acquired a second 32 drawer (+ a big drawer) unit, and a unit with 8 larger drawers, 8 small drawers, and a big bottom draw.
With tray partition, I now have a potantial 250 separate storage areas.

Bits_and_pieces_storage.jpg.41df871341ca2415d68ec71d6a6dcde6.jpg


Hahaha!
I know ... tray units are like a rucksack ... you always fill them 🙂

I then went to Weldom, and blew €9 on machine screws, lock nuts, washers etc.

Screws_nuts_washers_Weldom.jpg.d2fd5fc6452736921a15470c8391dfc0.jpg

It's pick & mix.
The above was 3Kg
I'm going to go back, and re-equip the workshop with pretty much everything that they have (another €18 should do it).
The scope needs screw and nuts.
I particularly needed 4mm nylon lock nuts, for the tripod, but also I'd quite like to use hex head allen key screws for aligning the 60 - 100mm adapter.
I was thinking 4mm, but they only have 5mm in allen key format ... fine enough, I reckon.

If you have never rebuilt your workshop ... I'd say 'go for it'.
Things get moved to where you know they will be better placed; rather than sticking with the ad hock organic growth, that sort of goes in any place available.

... and my poor spiders.
All their historic work, demolished like a biblical act.

Good.
They can build new webs, in time for the next mossie season  🌝

 

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  • 2 weeks later...

OTA Upgrade Begins & Material Issues

Balance Adjustment

The issue here is that I cannot accurately balance the scope by repositioning the pivot point, because this would require tube clamps ... a different mount system.

I decided to reposition the pivot point further up the metal tube, and leave the accurate balancing to the addition of weight.

The previous centre lines were kept, in order to avoid the pain of marking out a tube, that requires a height gauge scriber (it's on the purchase list).

A straight edge was used (and the eye), to project each opposing centre line, down the tube.
The dimensions were based around the 60 - 100 adapter overlap ... space was required for the lock shaft bracket screw; which then determined the pivot point.
(I could have reversed the lock shaft - I see that modern scopes have the lock shaft reversed - but I pressed on with the original plan)

The centre lines were roughed in using a pencil, and centre marked accurately using a carbide tipped scribe, against a steel rule.
Note: Buy one (carbide tipped scribe). They are only a couple of Euros, and you will wonder how you ever managed without it.

All the holes were pilot drilled using a cobalt 1.5mm drill bit.
The pivot holes were drilled with a 'P' (8.2mm)
The lock screw hole, with a 5/16 (just under 8mm)
The bracket holes, 4mm

Here is an image of the pilot holes, and finished 8.2mm - the scribe can be seen above the tube:

Holes_and_scribe.jpg.071a709766bf2197a335d39cefcd9f1e.jpg

The pivot brackets were then assembled (balancing the nuts on the straight edge ... a real pain).

Both faces were parallel to 0.2mm.
Perfect - no different to how they were originally ... and they are anyway scheduled for flatting.

All was going well; and then the first  batch of 304 inox arrived...

OTA Innards

The plan is to assemble the baffles and flocking, and insert them into the tube.
It seemed a brilliant concept (and still does); but I simply took a punt on the gauge of steel @ 0.4mm.

Er... don't do it.
I'm still awaiting the 0.2, and 0.1 gauge 304 inox.
However, as it stands, I'm guessing that 0.2 gauge will be ideal.

Bare in mind that 304 inox work hardens, simply by casually glancing at it.
Here's how it arrived (I had no idea how it would be packaged):

304-0.4-arrived.jpg.e0ceacad2ceb9e791cd8e2c40433a1cd.jpg

Oh dear.
At this point, I would suggest that you go to Sheffield for your inox.
I knew it ... but I was building a big order, and it was a straight €6.50 delivered ... so I clicked buy, and job done.

I can always talk to Sheffield, but hey ... overcoming problems can be satisfying (or painful & expensive) :icon_scratch:

It's a metre in length.
I need to form about 460mm into a partial tube ... yet it has been bent and work hardened the wrong way.
Therefore, the piece needs cutting to length, heating to cherry red, then quenching ... I can do that.

However, the thinking that the sheet could be simply sprung rolled into the tube ... no way - hence why 0.2mm would have been a better choice.

Okay; so I needed a cylinder of wood @ around 57mm diameter (a table leg, maybe).
I couldn't find one, and was forced to buy two rolling pins for a fiver.

Here's what you get for your fiver...
4 off file handles
2 off 5mm steel rods 270mm
2 off 57mm white oak cylinders 210mm (close enough).

Rolling_pins.jpg.507af085701f285ca38e5c4ce1ddcb8c.jpg


These were then epoxied together:

Rolling_pins_joined.jpg.11997036bbbee6034a9e8b30b3eba1f8.jpg

The Plan (it's fluid)

Drill holes along one edge of the steel, and screw the steel to the wooden cylinder.
... Wrap around the steel sheet (using as yet, an undetermined method) :grin:
... Wire wrap the sheet to the form
... Shot peen the surface - to force the external surface to stretch, and so force the curvature.

This latter concept is purely theoretical, but I am confident (?) that this will shock the already stressed steel molecules
... causing them to jump into a less stressed position, that will be curved.

Further heat treatment may be required; but by hook or crook, I'll get the tube inner made.
(You can see why I recommend 0.2mm thick inox over 0.4mm)

Anyway; that's for tomorrow, as the epoxy is now curing.

Cleaning The Tube

Remember those experiments with acrylic paint?
It's all got to come out.

I needed a 55 - 60mm rotary wire brush.
Didn't have one, so was forced to purchase:

Rotary_wire_brushes.jpg.a793ebe2b17323f8191c69872eb4fb61.jpg


I figured that I could run a 6mm thread die down the shaft, and using one of my newly acquired connectors, attach threaded rod, to get the brush down the tube.

Hahaha!
The die made no impression on the shaft.
I resorted to plan B.
That being to bond the 8mm threaded connectors to the shaft - trying as best to keep them central:

Rotary_wire_brushes_with_connectors.jpg.ad1958f99f3eb8a9e2a86efdca4fbe62.jpg


They are also curing.

The larger brush is on the limit.
I've squashed in the wires ... hopefully it will do the job.

Either way ... tomorrow I will have a clean tube, and (inshalla) a tube insert.

Pivot Bearing Surfaces

1 off 1 x 100 x 100 inox 304 has arrived.
How I cut and drill it, will be revealed when it's done.

🌝

 

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