Flocking a Synta 70mm f/13 Achromat

[Stub Mandrel]

28 minutes ago, Alan64 said:

                                     

You've missed a bit

 

Big difference, surely that will make a visible difference to observations.

 

[Alan64]

I do hope so.  At least that yellowish cast will be gone from the Moon.  I've got that last strip to place, but it will need to be measured, width-wise, and I'll be doing that after twenty to forty winks.

[Alan64]

Now that that's done, the next thing to be done before putting it all together for regular usage is to remove this, this Synta haze, and what looks to be polishing residue.  It's on the underside of the bottom, flint element, the flat side that faces the focusser...

It appears as a cloud, there.  This is what I'll be using to buff it off and out...

It has to be the original formula, that was sold for decades, here in the U.S. at least.  No varieties can be substituted, and there are quite a few.  I couldn't find it locally, instead having to order it online from an obscure personal-care website.  It has been used successfully in the cleaning of fouled camera lenses, and for quite some time.  I use only my clean fingertips to buff the glass, and you can press down as hard as you'd like.  An example of a 60mm doublet, a Towa from the 1960s, that was in far worse shape, and cleaned with the Pond's...

[Alan64]

I believe I have the doublet squared away now.

The other day I received my very first laser-collimator...

I have an operational Newtonian, the 150mm f/5, but it never prompted me to get one of these.  What did prompt me to get it: the refractor within this thread.  I got it primarily to collimate the focusser to the tube.  I know that I'll eventually stick it into the Newtonian in future, but otherwise I've had great success and ease in using a collimation-cap and a Cheshire instead.

The seller advertised this as now having a triplet-lens for the laser, and for a tight, circular spot...

It seems satisfactory.  But first, I will need to make a stand...and to collimate the collimator(!), if needed. 

Edited June 19, 2018 by Alan64

[Alan64]

I have the stand made for the collimator.  It took three days or so to make, and without being in a big hurry.  I would've made it of some nobler wood, but in that I'll only be using it once, twice, or thrice in my lifetime, I chose basswood and plywood instead.  I have seen the videos, tutorials, and the plumbing parts at my local hardware, and for making a stand...nah...  

The base was easy enough, but the uprights required more precision, and that afforded by my old Preac mini table-saw, which is renowned for that very thing.  I cut out the squares, one precisely the size of the other.  I then taped them together and cut out the "V" slots, simultaneously for each.  Before I separated them, I cut a small notch in the centre at the bottom, where they will join the base when glued, and so to accurately place them onto the centre-line drawn onto the base.  I installed one, then made a temporary spacer with the Preac, and then glued the other in place, with the spacer ensuring the squareness of the two in unison. 

But before I glued the first upright into position, I lined the "V" slots of both with narrow, self-adhesive strips of PTFE.  In order for the strips to stick well without coming off, clear-satin spray was applied to the surfaces of the bare wood, then steel-woolled, then  a few coats of gloss-lacquer applied on top of that...

They are the only portions of the woods of the stand that are properly finished.  I may shellac the rest of the stand in the end...

The upright on the right within that image looks to be leaning towards same, but it's not.  That's my Minolta instead.

 The collimator rolls ever so smoothly and evenly upon it.  I can think of nothing better.  I tried it out briefly, and the laser traced out a circle of at least 50mm in diameter upon the wall.  No matter, I'm prepared to collimate it, and however long it takes...

[Alan64]

The stand was complete to use initially, but needed improvement after that.  I eventually added a fixed stop at the front, and a spring-loaded one at the rear.  To keep the woods used from warping over time, three coats of shellac were applied...

  

The active-stop applies just the right amount of pressure, and to keep the collimator from falling out at the front whilst rotating it.  The stand works beautifully now, and the collimator touches no wood, only PTFE.  Before the enhancements, I had attempted to collimate the device using its set-screws.  At one point, I got it almost bang-on, but then in tweaking it further I only made it worse.  I then decided to remove the set-screws, and to explore the nature of the system.  The short one was under the label...

...hardly intuitive.  Why that one is shorter than the other two is beyond me, as it screws down to the same depth.  Perhaps they ran out of the longer ones at the time of its assembly.

In this case, I will not be using this collimator outdoors, nor for travelling; rather, in a laboratory-type setting, although a laboratory I do not have...

...just some things to get my fingers on.

Edited July 10, 2018 by Alan64

[Alan64]

The holes of the casing are not necessarily aligned with the threaded holes below.  The external thumbscrews had no trouble fitting into two of them, but one of the holes would not play nice...

I've since enlarged the area there with a diamond-bit, and an external screw will now thread into it.  I had to stuff a bit of cotton into the threaded hole to keep the metal "dust" from falling inside the device whilst grinding.  I had not planned for this, but it did work out nicely nonetheless, and in that the widest point of the heads of the stainless-steel screws will clear the upright whilst rotating the collimator...

The collimator is now ready to collimate.

Edited July 13, 2018 by Alan64

[Ricochet]

That is a nice V-block you've made there Alan, certainly better engineered than the four nails wrapped in flocking that constitute mine.

I recently had to recollimate my cheap collimator and so the following tips might be useful if all of these are constructed in approximately the same manner (however I notice yours takes one CR2032 while mine used 3x LR44):

1. Internally, there is a smaller metal cylinder that comprises the laser diode and the battery compartment. This cylinder is quite stiffly pivoted at the bottom end and the three screws at the top simply push against the sides of this cylinder to adjust the position. The pivot in mine is stiff enough to hold the cylinder in a fixed position without the adjustment screws being in use. You can use this to start your collimation procedure with the screws backed out.
2. Some sort of target or grid on the wall you are pointing the laser at might be useful so that you can more easily tell how far off centre you are at any point.
3. When collimating start with all the screws backed out so that they are not touching the internal cylinder. Rotate the collimator until the laser dot is at the lowest point of the circle traced by the laser. If you tighten the screw that is now top-most it will bring the laser dot upwards. Tighten the screw a touch and rotate the collimator again until the laser is at the lowest point in the new circle. Tighten whichever screw is now nearest the top. Repeat this procedure until the laser is collimated. You will probably find that you are only tightening two of the screws. Once you have the laser collimated carefully snug up the screw that you haven't really touched to lock the laser in position.
4. Don't tighten the screws too tightly as the internal cylinder is quite delicate and you could either deform the cylinder or cut through the plastic film that insulates if from the outer body and create a short circuit. (This might not apply if your adjustment screws push against a solid part and not the sides of the battery compartment like mine.)

Good luck.

 

[Alan64]

17 hours ago, Ricochet said:

That is a nice V-block you've made there Alan, certainly better engineered than the four nails wrapped in flocking that constitute mine.

I recently had to recollimate my cheap collimator and so the following tips might be useful if all of these are constructed in approximately the same manner (however I notice yours takes one CR2032 while mine used 3x LR44):

1. Internally, there is a smaller metal cylinder that comprises the laser diode and the battery compartment. This cylinder is quite stiffly pivoted at the bottom end and the three screws at the top simply push against the sides of this cylinder to adjust the position. The pivot in mine is stiff enough to hold the cylinder in a fixed position without the adjustment screws being in use. You can use this to start your collimation procedure with the screws backed out.
2. Some sort of target or grid on the wall you are pointing the laser at might be useful so that you can more easily tell how far off centre you are at any point.
3. When collimating start with all the screws backed out so that they are not touching the internal cylinder. Rotate the collimator until the laser dot is at the lowest point of the circle traced by the laser. If you tighten the screw that is now top-most it will bring the laser dot upwards. Tighten the screw a touch and rotate the collimator again until the laser is at the lowest point in the new circle. Tighten whichever screw is now nearest the top. Repeat this procedure until the laser is collimated. You will probably find that you are only tightening two of the screws. Once you have the laser collimated carefully snug up the screw that you haven't really touched to lock the laser in position.
4. Don't tighten the screws too tightly as the internal cylinder is quite delicate and you could either deform the cylinder or cut through the plastic film that insulates if from the outer body and create a short circuit. (This might not apply if your adjustment screws push against a solid part and not the sides of the battery compartment like mine.)

Good luck.

 

Thank you, but I had already collimated it prior to reading your post.  Yes, I knew that the laser-diode was encased somehow within, so I did not batten down any screws too tightly.  As for the target, about 5.5 metres distant, I taped a sheet of black art-paper onto a kitchen cabinet, and had the collimator on a desk in the living-room.  I perched(not attached) a pair of 7x50s onto a photo-tripod in front of the chair I was sitting in, and observed the spot whilst rotating the collimator.  When the spot didn't move any longer, I took it off the stand and placed it into the focusser of the achromat to collimate that.  That's done as well.  In the end, I used the black-oiled socket-head screws, which threaded in a bit tighter than the stainless-steel hex-heads, therefore there was really no need for any other parts to lock the screws in position, not for my purposes indoors...

It will never be taken outdoors for use, nor for travelling.  

I then placed the objective-cell onto the front of the achromat's tube, and collimated that to the focusser, but with a diagonal in place, and with my refractor-Cheshire.  Mind you, it's but a 70mm objective, yet I saw the sharply-defined Airy disc of Polaris and its blade-like first-diffraction ring...and at 225x(4mm).  I also used Polaris for the star-test, at 150x(6mm), and the intrafocal pattern was practically "textbook", so it appeared.  Extrafocally, however, it was a bit of a blur, and due to the seeing I suspect.  I'll be star-testing it further in future.  I do have some final tweaks to perform before the achromat is at last completed; the doublet's spacers mainly.  Also, the Celestron star-prism diagonal, the prism itself, needs blackening.