Gaining Focus - Upgrade, mod, or replace?

[Fo_Cuss]

Nicely Brushed Tube

The rotary wire brush came together nicely:

The difficulty is in clamping the tube.
Ideally, round jaws, or at least vee jaws should be used.
I had neither.

A soft jaw was reversed, to obtain two contact points, forcing the tube down onto the spine of the vice, and into the rubber of the other soft jaw.

It 'just' did the job, with a minor amount of slippage.

The problem is that the tube is squeezed, so it deforms from a circle to an oval.
Rotary tools don't like that, and they grab.

The pain is that the brush assembly is passed into the tube, then clamped in the drill chuck.
One pass can be achieved, and then the brush must be removed from the chuck, and the process repeated.

But it worked.
I now have a beautifully brushed tube:

🌝

[Fo_Cuss]

304 Inox !  Really ... Is this a wise decision?

It probably is, if you appreciate the school of hard knocks  😉

A few posts back, I voiced my doubts over the practicality of using 0.4mm 304 stainless steel, as a base for the telescope innards.

It is certainly a strange material.
... deforming, whilst being cut, and then work hardening.

Cutting to shape

The first task was to cut it to width, for rolling into an open tube.
This went well.
I settled upon slicing with an angle grinder.
After marking out the cut, the sheet was clamped to the bench, using 20mm deep timber that was positioned parallel, and away from the cut line.
This timber was to support the angle grinder head, to aid stability.

With that stability in play, I slotted the SS sheet.
Yes ... you heard correctly.

Hey ... we are talking about slotting a sheet of metal 0.4mm thick!
Masses of cutting sparks, while the slot formed and descended (in a 'U' shape).

The good news is that it did create a straight edge.

At a certain point, when beginning to break through, I stopped ... waggling the piece, to cause it to split.

The bulk of the 'flash' cleaned off easily with the grinder.
It was finished with a fine file - dragged sideways.

The ultra sharp flash can then be peeled off, and binned.

That method works ... I would use it again.

Rolling the tube

I don't have a 'break', or a rolling machine.
My previous concept of fixing the sheet to the cylindrical mould (rolling pins), was ditched in favour of ratchet straps.

The edges were covered with card, to protect the straps.

Strap loops were placed around the sheet, with the mould in the centre ... and then ratcheted.
This brought the sheet around the mould.

It worked; only that the cut edge had work hardened, so it didn't want to bend.

The plan was to replace the straps with wires, and then shot peen.
Instead, I called it a day.

• Note: Both tasks have been video documented for later publication, to aid the text explanation above.

Yes; I toyed with the idea of annealing the sheet, and starting again.
However, I was doubtful that full success would be achieved.

It is important to recognise when a plan is not correct ⬅️
... and in this case; the 0.4mm gauge was simply too thick for the tools at my disposal.

0.2mm will be fine; only that I have not really ordered the correct quantity for the task
100mm wide, when 160mm was the plan ... to form a slotted tube.
100mm forms just more than a half pipe.

It will work ... carrying the baffle assembly, with fixed flocking to the roof of the tube.
It may have to be that.

Or, I order the steel from Sheffield, and finish building the other elements of the scope.
Or, I make the innards out of cardboard ... sort of a shame, though it would create the same effect.

It's the weekend.
I have time to sleep on it ... and there is plenty to do.

Let's see what tomorrow brings  🌝

 

[Fo_Cuss]

What happened next ?

I'm a big believer in sharing knowledge and experience - it has been the big enabling win delivered by the internet.
I always try to keep my account in balance; taking information and giving back (after applying the received information).

Consequently, the next day (and feeling rejuvinated), with this in mind, I reflected upon what had been achieved.

Rolling any steel sheet without tooling, is a major challenge
... 304, over a length of half a metre, could (understandably) be considered madness.

Yet, I'd got pretty close, and I had the video footage (including the cutting to size).

The mental break had been made, vis a vis using the tube for the scope
... but I hadn't tested the concept of 'shot peening' to fix the radius
... nor had I attempted 'annealing'.

It was a new day, and the 60mm jubilee clips had been delivered - 2 off.
Hmmm!
Why hadn't I order 8 off? ... er ... cost, obviously (and I didn't know that I would need 8 off)

Time to try the bizarre 'garden weed burner' that I had picked up at Lidl for around a fiver ... I knew that I would need it one day

One is supposed to heat the entire piece to cherry red, and quench
... but in fact, 304 can simply be heated to cherry red.
Quenched is apparently better, but it is not an absolute requirement.

Using a butane torch, means that a small portion can be heated to cherry red, but this cools as the flame moves on.
... and it becomes very difficult to know, where exactly 'cherry red' has been achieved.

As it turns out ... it is not too critical.
From the photo below, you can see that I did not achieve an even 'heat' ... yet thankfully, it annealed.

A plasterers tub contained the water, so it was quenched.
... and then assembled onto the rolling pin form, again using a ratchet strap in the middle, and a jubilee clip towards each end.

The assembly was then shot peened - obviously avoiding the straps.

The result was encouraging ... particularly where the jubilee clips had been used.
... and the shot peening HAD fixed the curve (to a significant degree).

We now had a half-pipe.

The lower half was correctly curved, but above the centre-line there was a band of steel that had not rolled
... except for where the jubilee clips had been attached.

Proof of Concept

Time to reflect upon what had been learned

Clearly, a lot of jubilee clips would help matters
... but having a sheet width that was larger than the circumference, would provide an overlap, that would clamp & roll the edges.
As such, it could be rolled with one overlap, then re-rolled to overlap the opposite edge.
OR
A length of sheet could be placed over both edges, to force both edges into a radius (aha...)

This morning, I was mulling these details, when my eyes alighted upon the scrap strip of 304 that I had recently parted.
Wow!
Maybe it would be wide enough to cover both edges (yes)
... and what about photographing it, to show everybody how a 0.4mm sheet of 304 grinds and forms a 'U' channel.

After cleaning off the flash, the scrap strip of sheet was inserted over the tube edges...
(just fitted ... phew!)

... and pushed down the length.

Applying the lessons learned...

• Ratchet straps worked
• Jubilee clips worked better
• Shot peening worked

Okay ... time for detailed work.
I decided to fully commit to the task.
It was now or never, to prove that 304 could be rolled into a tube from flat sheet, without a rolling machine.

The principal strategy was to strap the tube to the form, using ratchet straps and jubilee clips
... with the jubilee clips centralish, spaced at around 80mm apart.

This 80mm section of tubing would be micro-peened.

The assembly would be then blown off, and the jubilee clips repositioned, with one clip just on the peened surface ... the other around 80mm distant etc.

Hammer Peening

How could I forget?
Don't forget!

Hammer peening provides two major benefits:

• Breaks the grab friction of the strap, and the tube (on the form)
  ... enabling two more tightening turns on the jubilee clip 👍
• Enables the edges to be peened through the scrap strip (inaccessible to the peening machine)
  ... locking in the curve that has been formed (could this be it?)

Note:
I also used a high tech peening machine.
You are most likely at best, to have a sand blaster.
If so ... shot blast media can be purchased, and this will do the job.
Otherwise, you can use a common or garden 'peening hammer', to lock in the curve.

The thinking coalesced

How many times have you been doing something, when your thinking coalesced?
It's normal.
That's why the last part of the wall (that you built) is better than the first part.

Otherwise known as 'getting the hang of it'.
Which I did.
... with the edges getting an ever increasing beating (to the levels of 'If'  )

Here is the final config, as it came out of the Peenmatic 620S...

Looking good.
... but would it be round?
... would the edges have rolled?

Results

Hmmm!
Not perfect.
However; not too bad for a first attempt at hand rolling steel (never mind 304 inox).

It measures 63mm diameter at one end (the last end worked on), and 65mm diameter at the end that I started with.

Clearly, the edges have not fully rolled
... but they have been rolled 👍

Transport for the baffles?

At median 32mm radius it grips like something that grips a lot.
However, the baffles will be bonded within the transport tube.
This presents the opportunity to form the radius to 30mm.
(say, clamping the tube to the baffle, with a jubilee clip, during epoxy curing.)

One thing is certain ... I will have more than sufficient baffle material.
Therefore, this transport tube can be built up with baffles ... allowing a 'free attempt' to be made.

What a great back-story for the scope, if this tube can be used 🙂

Final Thoughts

If I can make it happen, I guess it will be the only scope in existence with a hand rolled baffle transport mechanism.
The sensible option would be to have a sheet metal worker roll one with rollers.
Or even easier ... simply buy a 60mm diameter tube in aluminium and slot it with snips, or a jig saw
... perfect in 20 minutes!

But ... setting off on a voyage into the unknown (and sticking with it), can also be fun and enlightening.

The hardest times are remembered the fondest 😉

🌝

 

Edited January 27, 2020 by Fo_Cuss

[Fo_Cuss]

A daft error - Misaligned lock shaft clamp

So there I am, examining, and thinking about the azimuth mount (what a heap of....)

I'm actually considering how best to reinforce the slanted 'U'.

With the scope being extended, there will be an increased 'twisting' force, centered just above the lock-shaft clamp.

The primary force will be along the scope clamp centre line
... but this will passed to the legs of the 'U' ... finding the weakest point, which is the horizontal centre line of the legs.

Obviously, the rigidity of these legs must be increased
... but we have the pathetic screw length

... which leaves very little room for increasing the thickness of the leg.
(this is really annoying)

Consequently; I was looking at this in detail, and considering adding the 1mm sheet inox, to both sides
... and doing away with the washers.
Nice idea!
When I suddenly realise, that the lock shaft is 'sticking out' at a bizarre angle.

How?
How did I not see this earlier, when modding the clamp bracket?
( tunnel vision, I'll wager 😉 )

To get a visualisation of the error, I used my 'P' drill.

• It's shameful.
  My 'P' dill bit is around 45 years old ... very high quality
  Yet I've allowed rust to gather on it's surface.
  Embarrassing.
  It will be treated with phosphoric acid (and be born again)

Realignment (sans milling machine)

There's always the 'side of the drill bit' method.
... only the alignment is a long way out; beyond a bit of tickling.
It had to be a grinding bit.

Ahaa ... I had one.
8mm dome head, but wildly innacurately bonded to it's shaft.
... though easily dressed.

With the cylinder perpendicular in the vice
... the 'clamped to' side was releaved of it's erroneous slant.

What a load of messing around, to repair a production error that may even have been produced purposefully (to avoid the need for spacers at the scope tube end).

Anyway ... it's done now 👍

🌝

[Fo_Cuss]

The Azimuth Mount - Created Anew !

Someone is watching over me 😉

It must be the case, because I fell upon some beautifully soft, box section mild steel.
Oh ... I needed it, as I was going to use angle iron (which is a different beast altogether).
Just thinking about it, makes me thankful.

I could cut it like butter with a hacksaw, or jig saw.

Here it is being cut, after marking out :

The plates cut, drilled, and formed :

What's the formed curve for ?

Hahaha!
A moment of madness, when I thought " c'mon ... add some form over function "

I accept that I am useless at pointless design.
For me, the function provides the beauty (but anyway, I added a curve) 🙂

How was the hole drilled ?

This is an engineers technique worth knowing.

The hole obviously had to be drilled in the exact position, to match the hole already drilled in the azimuth mount.
The hole was scribed, and the drill hole was repositioned PRIOR TO FULL DIAMETER PENETRATION.
A centre punch was used to impact a hole into the edge of the initial chamfer, to cause the drill bit 'to walk' in the direction of the centre mark.
(If it's a long way out, you can impact a slot in the chamfer wall)

In this way, the hole was positioned perfectly.

Azimuth mount plates bonded :

I allowed the plates to slightly ride on the epoxy bed.
I could have adjusted the edge, but the shoulder provided additional bonding support, so it was left as is.

Making Parallel :

With the plates added, I needed to bring the faces parallel.

Understand, that if attempting this mod; the area with the least metal will be cut the most.
Therefore, the open end of the mount (to the right), had more metal removed.
Hence it was blacked with a permenant marker.

The dark band visible at around 9:30 O'clock was the high point.

I got it parallel to within 0.2mm across the 45mm diameter... good enough, as more work was to be done.
(and a very slight twist of the thumb screws would lock it parallel)

Horizontal Pivot Plates

Marked out & drilled

These were made out of 1mm 304 inox.
First marked out, and drilled using Rocol RTD cutting fluid :

They were then cut with a jigsaw.
Note how the plate was well clamped.

Cutting with a jigsaw was a nightmare, as at 45mm diameter, the curve is too tight for the width of the saw blade.

You need to arc past the tangent, then nibble a gap, to allow the blade to turn in.
(or cut hexagonal, and trim later)

Rocol RTD cutting fluid again used.

Here is how they look, before and after initial trimming :

Here they are, after final trimming, and 'hand ground' flat :

... and being bonded :

Support screws were then ground :

... and bonded in place :

Metal repair filler was then applied

This was carried out in four phases, building the filler gradually :

3rd Filler Phase :

4th Filler Phase

Note how the filler was piled higher than need be.
This is necessary, to ensure that the final cutting can be accomplished.

Here are two images of the completed azimuth mount reinforced pivot plates :

Final Measurement

This was always going to be of concern, due to shrinkage of both the bonding and the filler.
... and with baited breat, I measured.

Phew!
0.2mm difference between the bottom and top of the plates.

Ideal for full lock, when using the thumb screws, while offering excellent friction for controlled movement of the scope.

Wow!
What a journey that was.
AND they look great ... hahaha ... form AND function

🌝
 

Edited February 10, 2020 by Fo_Cuss

[Fo_Cuss]

Horizontal Azimuth Damping
Pan Gauge
Two extra spindle clamps

Horizontal Azimuth Damping

Do you remember those old leather boots that you threw in the back of a cupboard?
... it's payback time 😈

Top right ... you can see where the leather was removed.
This is strong hide leather, 2mm thick.

While you are at it, remove the tongues ... they are 1mm thick.

The leather appears to be in an unusable condition
... but this all changes, when washed and scrubbed in warm water.

Stretch the leather pieces out on tenta-hooks (or cable clips 😉 )

Leave them a day, to dry out.

Locate an appropriate flat drill bit, to cut the internal diameter of the damping washer.

Cut so far, and finish with a very sharp knife
... and gain a spare leather washer, to be stored for future projects 🙂

Cut off the piece, leaving more than sufficient width for the washer.
Then thin (if required) using a bench mounted angle grinder.

Fit the damping washer to the spindle, and grease.
Press the azimuth mount into the tripod head, rotating the mount.

Trim the corners, ensuring that the leather damping washer is projecting out, when assembled.

This additional width will provide support for the washer, and prevent it from being squeezed apart, when in use.

The leather damping washer provides the ideal material for resonance isolation between the scope and the tripod
... and excellent friction control for panning the scope 👍

Pan Gauge

Buy a brass drawing compass off eBay (for a couple of euros).

Install in your pedestal drill, a boring tool to match the outside diameter of the tripod head bearing.

With three screws, attach the brass compass to an appropriate piece of wood - grinding off the screw points (if required).

Mark off the drill centre (for the arbour), or use your best judgement.

Adjust the drill speed to low
... and cut an arc into the brass compass.

Offer up the piece to the tripod head
... and clean up, to fit.

Then bond the gauge to the left, or right of the tripod head (when the tripod is set to the user position - typically with one leg forward).

Buy an appropriate sized pipe clamp, which has a threaded attachment element

The thickness, or band width, must be reduced equally (on either side of the attachment element), in order for it to fit the available space of the azimuth mount 'spindle shoulder'.

Locate a bolt that will fit through the attachment element.

Using a bench mounted angle grinder, and a bench grinding wheel...
Undercut the hex head, converting it into a chamfered head
... that will fit in the pipe clamp, without interfering with the internal diameter.

Flat the bolt threads, and drill a hole to match any stiff rod available (typically a cleaned up welding rod).

Using a vice and hammer ... put a 90 degree bend in the rod.

Assemble all pieces.

Set the height of the rod
... and bond the rod to the bolt, as required (prior to cutting off any excess).

Dissasemble, and degrease the compass.

With rags to hand
... spray the visible compass surface black; and immediately wipe off the paint.

A hair drier will speed initial drying, allowing a second coat to be applied almost immediately, before again, wiping off the paint.
... this to provide contrast for the gauge markings.

Note : Out of chronological order....

Add two extra spindle clamp threads

Before all the above ... mark and drill two equidistant tapping holes
... tapping the holes to suit the additional thumbscrews.

Punch a similar sized diameter from a sheet of PTFE.
These round pieces are to allow the spindle bearing to be clamped, without damage
... all as seen assembled in the above image (that shows the blacked brass compass).

Nearly there, with the azimuth mount.
Just the main spindle bearing, the tilt damping washers, and a lick of paint....

🌝

Edited March 5, 2020 by Fo_Cuss

[Fo_Cuss]

Tilt Damping Washers & The (perfect) Spindle Bearing

Tilt Damping Washers

Easily and quickly made, once the leather has been staked out.

A new blade in the Stanley knife, is best for tough hide.
Then a hole punch to suit the clamp screws.

The (perfect) Spindle Bearing

This requires PTFE sheet - 0.4mm should be ideal, assuming the sloppy play in these bearings is universal.

Determine the bearing circumference, and height.
Cut the strip of PTFE short in circumference, by 2mm
... and short in height by 4mm.

Wrap the PTFE inside the bearing tube (tripod head), centrally positioned, with the gap between two clamp screw holes.
Using silicone spray, coat the azimuth mount spindle.
With the leather damping washer fitted ... insert the spindle into the bearing tube.
Simultaneously, press & rotate the components together (with force).

You should see a gap between the leather washer face, and the bearing face.
(if not, you will need a thicker sheet of PTFE)

The objective, is to force the spindle home, compressing and stretching the PTFE.

Initially, manually rotate & press repeatedly.
... you will make good progress.
This is due the bearing being formed to the uneven surfaces
... necessary, to facilitate the next phase.

Grab a copper & hide hammer.
A No. 2 size will be ideal for the task
... not overly heavy, and therefore easy to control.

Place the flat underside of the tripod head, onto the anvil of the vice.
Using the hide face of the hammer, with minimal force, strike the base of the U bracket (azimuth mount).

You will have to get a feel for the force that you use.
Hit it too hard, and you won't be able to rotate the azimuth mount.

Wedge the tripod head in the vice, and rotate the azimuth mount.
... repeat a couple of times, before separating the pieces.

Examine the PTFE bearing (shell), in situ.

In places, the circumference may be close to joining.
Expect it to be uneven due to the uneven metal surfaces.

Note the position of the PTFE shell.
Before the next pressing, it should be refitted with the gap between the clamp screw holes (the same position each time).

Clean off any metal residues.
If the shell circumference has become joined, before the spindle is fully home
... with sharp scissors, snip a mm strip from the circumference.
This will allow more expansion space.

Clean the spindle, respray with silicone, and assemble for the next round of 'tap n turn' 😁

Continue in this manner, until the spindle & leather washer finds home.

At close of play, the PTFE shell may be fully joined, though this is not critical, as the shell will not rotate in the tube.
It may look something like this:

When complete...
In the lteral sense of the word; you will have created the perfect azimuth mount bearing 👍

The list of benefits is impressive:

• Rotational accuracy
• Exceptional stability (due to bearing interface height)
• Smooth 'friction rotation'
• Resonance flow barrier (zero metal contact)
• No 'lock movement' after locating the object to be viewed

... and in so doing; solved one of the major blights of telescope users the world over ✌️

🌝

[Fo_Cuss]

Pan Handle

Hahaha!
What else do I call it?

The scope pans and tilts, and ideally needs a handle for both operations.
This one deals with the panning operation, so ... it's the 'pan handle' 😀

Sourcing the material

One really needs a recycling centre that allows exchange.
Bring something in, and take something out (for repurposing).

This 'life balance' pays dividends (is it a game?)

It has got to the stage, where I now expect my needs to be fulfilled.

There was a beautiful 'big' piece of angle iron in the centre of the skip.
It was there just to tempt me.
I knowingly refused the option ... and as I moved to the other end of the skip, a lorry backed up and covered the angle iron (closing the option)
... however, I had made the right choice.

At the other end of the skip were two lengths of machined stainless steel bar
... radius ends, with the most perfect chamfered slot (at the end) that you could ever hope to see.
I could already envisage 'chamfered screw heads', locking the bar to the azimuth mount.

🙂

Inox Bar

It needed some work, to form it to purpose.
Annoyingly, I didn't get a pic of it first.
It had a right angled bend at the opposite end to the chamfered slot, but at that end, there were two holes for attaching a wooden handle.

Applying heat to the bend, I straightened it out, to leave a kink (for strength).

In order to position the handle for ergonomic use, the bar needed bending out (away from the scope)
... then bending in (further down the bar), to bring it to where the hand would fall (when operating the scope).

These two bends were applied cold, in order to work harden the steel, and reduce flexing.

The image below, gives you an idea of the steel, with straightened kink at bottom right
... and the two positioning bends that were made:

This next image, provides a better 'top down view' of my chosen angles, and a better view of the kink:

Next, you can see the chamfered slot 'to die for', and the visible reminder of the fact, that the steel was bent in a vice
(a job for my peening machine, if I can get around to it) 😉

Here is the bar, fixed to the azimuth mount.
I simply scribed the slot, centre punched, and drilled two clearance holes.
Also note the first glimpse of the blacked and laquered azimuth mount (with the sultry pivot plates looking sooo nice):

Here it is mounted:

Making the wooden handle

I knew that I had a piece of an old wooden handle.
Perseverence paid off ... I unearthed it.
Now it needed slotting ... but how?

The little known fact amongst the general public, is that hacksaws are designed to hold multiple hacksaw blades
... typically 5 or 6 can be fitted at a push.
I needed just 4 blades, to do the job:

Sure, they are normally for slotting steel, but they will also slot wood:

A perfect fit, requiring a 'tap in':

The holes already present in the steel, were marked off on the wood, and then drilled.
The freshly cut wood was stained, and the whole handle was given a stained wax treatment
... to end up looking magnificent:

Yes, I know that I can tidy the edge, and maybe even fill the slot (though I doubt that I will).

The plain fact is, that you can hear the old wood screaming out ...
YES! ... A purpose in life AGAIN!
... and the steel saying "I'm with you there, mate" 😉

Hahaha!
An engineer should have empathy with the materials that he uses 😁

🌝

[Fo_Cuss]

OTA Assembly

Three pairs of clearance holes were drilled, equidistant around the 60mm - 100mm adapter.
The surface around these holes was severely abraded, using a grinder and emery cloth.

 

Six nuts were to be bonded over the holes, so each was also roughed up.

 

Six screws were wrapped in cling-film, prior to the nuts being assembled over the cling-film.
In pairs, two part epoxy was rubbed into the abraded surfaces of the adapter and nuts
... enabling the nuts to be bonded to the adapter.

 

When each pair of nuts was sufficiently cured, the screws were extracted (leaving the cling-film in place, for later removal).

 

Once all six nuts were fully cured, the scope was assembled for collimation testing.
As can be seen from the image ... collimation was achieved.

 

Here is the first image of the fully assembled scope with lens

 

OTA Bonding

I didn't think this through!

Conical set screws had been purchased

 

Six small location holes were drilled into the 60mm tube.
The intention being to adjust the scope, as per the hex screw setup.
What a stupid concept!

Of course the conical screws locked into the holes, and full adjustment was impossible.

I should have also acquired dome headed set crews, or set screws with a ball bearing at the tip.
One location hole should have been drilled (to provide a pivot anchor)
... allowing the positioning set screws to float into their appropriate positions.

Instead, I had to mess around (for ages) slotting the holes with a jewellers file, until the OTA achieved collimation.
Note: The original steel baffle from the scope tube, was placed at the tube end, to prevent deformation of the tube circumference

It wasn't great whilst doing it, but at least there was the benefit of six set screws penetrating the adapter.
IE. it was well locked to the tube.

For the bonding, I had a new tub of extra strong body filler called metal repair (Répare Métal by Sintofer).
Very smooth paste, without fibre glass strands (armoured).

If you intend to carry out a similar mod ... don't use armoured filler.
It is very important to use a very smooth paste, as it must be rapidly squeezed into a tight gap.

To carry out this task; the applicator edge was formed into an arc, to match the tube circumference.
This was achieved using a sharp knife, by scraping the knife across the plastic.

Sections of wood were clamped to the bench, and 20mm of packing was placed under the scope tube.

The wood, running parallel with the tube, allowed the tube and adapter to be rotated, without it slipping all over the place.
The packing ensured that this rotation did not stress the adapter.

I then repeatedly practiced the action, in order to get my hands accustomed to the movements, and the turning of the scope.

If you have ever used filler, you will know that the clock starts ticking, the moment that the hardener is mixed.
... it's highly stressful - particularly because the paste must penetrate sufficiently into the gap, around the entire circumference.
This to prevent warping, as the filler sets.

Without the practice trial runs, I doubt that I could have done it.
As the final gap was being filled, the paste began to stiffen.
I got the job done, with zero time to spare 😎

Once set; I checked the collimation
... and with huge relief, discovered it to be true (the relief IS palpable as I write this account).

The gap from the 100mm side, was then filled.

 

Apart from some cleaning off ... the job was done.
The heart of the new OTA was permanently assembled 👍

🌝

Edited March 7, 2020 by Fo_Cuss

[Fo_Cuss]

Flocking like a pro ... before getting baffled

Stray light absorption

I tried Black 3.0 on the inside of the scope tube.
The problem is that it doesn't perform that well with 'low angle' glancing light.
Rather than being absorbed, the photons merely bounce off the surface.

It is excellent for small difficult areas (so it is definitely worth having, and using).
However, for the tube section; material flocking will absorb a greater proportion of the photons.

Having said that; the 'bouncing bomb effect' still persists...
Hence, for those who are wanting to create a scope to the level of a scientific instrument, there is a need for baffles (to stop the light dead in its tracks).

We are going down the 'hyper-scope' route
... vibration free, and the 'black abyss of nothingness'  🔭

Consequently, the die is cast, for us.

... but from reading the many pages of SGL, I reckon that for most users; a straightforward flocking of the scope, will be sufficient.

Below, is my take, on this task....

Flocking Material

I went with the material recommended by johninderby.
Veloursfolie made in Holland, and retailed by https://www.firstlightoptics.com/misc/black-velour-telescope-flocking-material.html

 

fozzybear recommended felt:
https://www.feutrine-express.fr/product/Feutrine-metre-adhesive-Noir-0148#content

I had to choose one, so I took pot luck, and went with the first recommendation.

Points to consider when purchasing flocking
(lessons learned)

1. Photon absorption efficacy
2. Lint stability
3. Sticky backed
4. Thickness
5. How it is rolled

The veloursfolie achieves the first three objectives.
Fozzybear would not have recommended the felt, if it lacked efficacy and stability (and it's sticky backed)

Therefore, the key questions are 'thickness' and 'roll method'.

Thickness
If fozzybear is reading this, he might gently run a vernier over the felt.

The felt is spec'd at 1mm thick.
The veloursfolie is 0.5mm thick.

For me, this small thickness was useful, because in certain areas, I was tight for space.
However, my guess is that the extra thickness of the felt would pay dividends, in terms of supporting its own radius
... something that I would have benefited from (as will be outlined later)

The felt will also provide superior insulation, and better moisture absorption.
Therefore, if the budget runs to it ... both variants will be worth purchasing.

Roll Method
From a flocking perspective, the French win this hands down.
The felt is rolled internally.

The veloursfolie is rolled externally (the opposite of what is required).

This means that the veloursfolie must be bought in advance, hung, heat treated, re-rolled, heat treated, and left in a sewage pipe (preferably without sewage)

Here is what it looks like when it was simply re-rolled, and heat treated (hair drier) in a sewage pipe.
Clearly, when the rolling is reversed, the material is larger than the paper backing, so it must ripple.

Hence why I realised that it is probably better to let it first hang flat, using a hair drier to aid the movement of the bonding material.
... then roll it into a tube, and again blow hot air through it.

By my estimation; this will reduce the rippling.

Another (superior) method might be to use a warm iron (and some paper for glide and insulation), with the velour on a table.
This would squeeze the velour across its backing
... then re-roll it in a tube, and use the hair drier.

This re-working of the velour, will cause it to be bigger than the backing paper.
Trim off the excess, or make sure that you measure to the velour not the paper.

YouTube Flocking application

First watch a few YouTube videos of people attempting to flock their scopes.
They invariably recommend cutting the material into strips
... yet they still manage to plunge themselves into an impossible mess.

The reason is because they attempt to apply the sticky material 'dry'  🥴

Of course, the material is floppy, it touches the surface, it sticks, it's pulled off, it stretches.
It's a nightmare.

Don't do it this way!

Flocking application - the pro method

If the tube to be flocked, is too small to get your hand and arm in...

Find a tube, smaller in diameter to the tube to be flocked (a rolling pin maybe)
... or a cut off length of broom handle
... or something that can reach at least half way down the tube (for access from both sides).
... something that might be needed to apply pressure to the flocking material.

Take a spray bottle - say, one used for household surfaces.
Fill it with water.
Add a few drops of washing up liquid (not much).

This will prevent surface tension in the water.
IE. It will prevent globulation, and allow the water to 'wet' any surface.

Test the solution on an offcut of the flocking material, to confirm that the glue becomes fully wet
... adjust the detergent accordingly.

Measure the internal bore of the tube to be flocked, and subtract 2 x the thickness of the material
... to gain the correct internal circumference of the flocked tube.

Mark off, and cut the entire section - circumference by length (a guillotine is ideal for this).

Degrease the bore, and repeatedly mop it with the mild detergent solution.
If it is a hot day, then cool the tube, or leave it soaking in a tub of water.
The bore surface should be damp.
IE. It should be wettable.

If the water just glides off the surface, then wash it first with a strong soapy solution
... rinse, and apply your spray.

Remove the paper backing off the material in stages, wetting it as you go (so that it doesn't stick to your fingers).

If the water is gliding off the sticky glue ... gently rub the solution across the glue surface.

Check the tube, to confirm dampness ... give it another spray & mop, if required.

With the glue fully wetted, roll the material into a small diameter, and drop it in the tube.
Lay the tube horizontal, with the material joint at the top.

If needed ... manipulate the material edges, so that they lock together.
Rotate the tube so that the material joint is at the bottom.

Most of the water will be forced out by the material forming its circumference.
Any bumps will contain water.
Squeeze them out, using your hand, or your predetermined tool.

Heat the tube internally and externally with a hair drier, until you are fed up with the task.
Job done!

... and it's way quicker than the time it took to write this explanation.
... and you will have a perfectly flocked tube.
... and it is a stress free task (always appreciated).

Here is what it should look like, after flocking:

Very nice ✌️

🌝

[Fo_Cuss]

Baffle Assembly & Testing

Preparation

We can cast our minds back to January, when the final roll of the Baffle Transport Mechanism was completed.

The BTM had been put on the back-burner, in the hope that the lighter gauge inox sheet would offer an easy 'self roll' option.

It didn't!

All the effort would have had to be reproduced.
Surely easier, the second time around, but even still....
The task was enormous, and the challenge hadn't changed.

In fact, it was worse, because the first attempt was begun under blissfully ignorant conditions (perfect when setting out on a project).

No!
We have the hand rolled tube.
It fits.
... and it's as good as it needs to be (so let's crack on)

First task was to implement a method to retrieve the BTM from the original tube.
For this I chose an extended nut, to be bonded to the BTM.
First abrading both the nut and the BTM surface, before epoxying the nut in place

With the BTM in position
... the joined rolling pin assembly, was inserted, in order to support the BTM while it was being drilled for the scope mounts, and lock shaft.

After the usual abrasion, the scope mount nuts, and lock shaft nut, were bonded in place.
The lock shaft nut was thinned, to minimise blocking of light.

My advice would be to not bother with the scope mount nuts.
The epoxy bonding to inox, is so poor that it is far better to modify some large self tapping screws, that will bite into both the tube and the BTM.

Focal length testing

I wanted to place a baffle on the 'moving' focus tube.
Consequently, I needed to assemble the scope with what I had, and make a few test observations of the wind turbines.
The weather wasn't great, but the results were very encouraging
... I couldn't quite read the text on the side of the turbine fairings; though it was close.

The tests indicated that, with Mirror and Barlow, the focus tube had only 10mm remaining movement.
Mirror alone = 25mm
Barlow alone = 90mm
Direct = 100mm

There were some minor changes between the 12mm and 4mm eyepieces, but '10mm available movement remaining', was the max.

Baffle dimension calculation

From these tests, I could measure the focus tube penetration into the OTA
... and from this; calculate the baffle internal diameter.
... this based upon the available lens diameter of 90mm (from 93mm), and the focal length of the lens being 1000mm.

Using this knowledge, I programmed a spreadsheet, that would enable me to generate the intersection of the cone of photons, at the desired intervals for the baffles.

Underlying maths
Lr/FL
(90/2)/1000 = 0.045mm cone radius change per mm from the lens

I was measuring from the eyepiece side of the BTM (not installed in the scope).
Therefore, the scope and BTM were assembled, to gain the measuring datum edge.

Baffle 1 is the baffle attached to the end of the focus tube.
Baffles 2,3,4,5 are carried by the BTM.
Baffle 6 is the baffle attached to the 100mm scope tube, joined in the inox adapter.
Two spare calculation lines were for experimental purposes.

The 'Actual Baffle Diameter' is manually entered, based upon the calculated photon cone.
This to allow for a margin of error.

Creating the baffles

I used stock card, of a thickness that enabled laser printing.
I had it, so I used it.
The better route would be to buy the thickest card available.

I used a glue stick, to assemble 3 layers of the formed card.
The better route would be to use epoxy resin, and more layers (or much thicker card).

The baffles were sprayed 3 coats of black, and 3 coats of lacquer.

For experimental purposes, the baffles were oven dried.
I expected some warping, and was not disappointed.
The warping is inconsequential to the task ... but I would recommend using a hair drier.

The baffles were offered up:

The flocking was cut to size, with the backing best removed by inserting a Stanley knife blade.

With the baffles flocked, and the BTM spray-blacked
... they were epoxied into the BTM at their appropriate positions.

The BTM assembly was then inserted in the scope, for initial testing.
This being achieved with imaging that was 'normal exposure' 'over exposure' 'extreme over exposure'.
The principal being, that if photons are passing the baffles, they will be revealed by over exposing the images.

Note: Stray photons were expected around the baffles, but of interest was the reflection off the internal baffle edges.
These edges were then filled with Black 3.0 ... the success of which, can be judged at the end of this post.

The 'end tube' baffle was cut from 4 layers.
Each layer was soaked on both sides, 3 times, with lacquer.
The card could absorb no more lacquer.
On the 4th occasion of lacquering, the cards were assembled (bonded with lacquer).

After touch drying, the baffle was wrapped in wax paper, and placed under a heavy weight (overnight)
... and subsequently flocked, and bonded to the 100mm tube.

BTM Flocking

Nightmare!
Absolute nightmare!

If I had fabricated, more robust baffles, with more card, and epoxy resin ... it would have been far simpler.
But I didn't.
Therefore the bonded baffles could not hold the 'spring' of the rolled BTM.

This meant that I was having to constrain the 'BTM spring' with tape
... which restricted access when flocking each compartment.

I knew exactly this past error ... but I was not about to stop and repeat the very long process of fabricating the baffles, and bonding them etc.
They were in the BTM.
I had to somehow flock the damned compartments AND cover the open length of the tube (it makes me cringe, as I remember this task).

Thank goodness I had developed the 'wet application' method.

I removed the backing on each side of the central strip.
That strip would remain with paper, to (hopefully) self support the radius, across the open section of the BTM.

Each section was wetted, as were the glue sides of the flocking.

I think that the felt would likely have been easier to work with
... but they went in

Final testing of the baffles

The OTA was assembled, and image tested using the aforementioned exposure test:

Normal Exposure Image Test
Zero stray photons.

Over Exposure Image Test
Zero stray photons.

Extreme Over Exposure Image Test
Zero stray photons.

VICTORY!!! 

The few hours that it has taken to write up this post, is nothing compared to the weeks of effort that it took to achieve this success.

You might think it madness (I wouldn't argue)
... but our needs include daytime imaging, when stray light will be severely problematic.

As mentioned previously
... flocking and baffling to this extent, may have little impact upon celestial observation.
I'll leave that judgement to the more experienced astronomers....

However, the detailing that I've provided, should enable similar success for a small proportion of the effort that I expended.

Primarily; avoid rolling the tube.
Get a tube, with a slot, that has no 'spring' ... and then your work will fly.

For the section flocking
... flock each section with a single piece, and flock the entire length of a 0.1mm sheet, to be inserted in the gap, over the stronger epoxied baffles.

Hahaha!
Learn from my prototype.
That's what prototypes are for

I'll leave you, staring into the black abyss of nothingness (nice!)  😎

🌝