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A SkyScope of My Own

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#1 The_Vagabond

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Posted 15 December 2020 - 08:54 PM

After weeks of waiting, my SkyScope arrived today. The box was crushed (it looks as though something fell on the side they marked "FRAGILE"), but the telescope was in good shape. 

There is much to do in the weeks ahead, but this telescope is fairly complete. 

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Edited by The_Vagabond, 15 December 2020 - 10:07 PM.

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#2 The_Vagabond

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Posted 15 December 2020 - 08:56 PM

I have a lot going on at the moment, so this project is going to be touch and go until at least January. I did decide to clean up the forward brass tube ring (it comes off fairly easily, something I will rectify). While not a mirror finish, it'll do. 

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#3 The_Vagabond

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Posted 15 December 2020 - 09:00 PM

Sadly, this instrument has all the hallmarks of having been stored in less than ideal conditions. Not only did the finder scope literally have a spider's nest in it (spider long gone), but the forward part of the paperboard tube is "soft". This is why the forward brass reinforcing ring came off so easily, but it is especially bad under the focuser. I'm suspecting there will be a bit of work needed here. 

Also, the secondary is in rough shape. 

 

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#4 photomagica

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Posted 15 December 2020 - 09:19 PM

What a great find!

It is possible to stabilize and stiffen paper or paperboard using multiple coats of well thinned varnish. I have also used shellac, however it is not as moisture stable as varnish. By thinning the varnish you improve penetration. The varnish will glue all of the layers of paper solidly together. I start with a coat that is about 2/3rds thinner to achieve the best penetration and apply generously until the board is as wet as possible. After a couple of coats of that I apply a couple of coats thinned 50/50. When that is thoroughly dry I assess what additional coats may be needed. Most any kind of varnish that can be cut with mineral spirits (Varsol or similar) is fine, except avoid spar varnish as it is designed not to get really hard. Ignore any "do not thin" advice on the can.

Bill


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#5 The_Vagabond

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Posted 15 December 2020 - 10:05 PM

What a great find!

It is possible to stabilize and stiffen paper or paperboard using multiple coats of well thinned varnish. I have also used shellac, however it is not as moisture stable as varnish. By thinning the varnish you improve penetration. The varnish will glue all of the layers of paper solidly together. I start with a coat that is about 2/3rds thinner to achieve the best penetration and apply generously until the board is as wet as possible. After a couple of coats of that I apply a couple of coats thinned 50/50. When that is thoroughly dry I assess what additional coats may be needed. Most any kind of varnish that can be cut with mineral spirits (Varsol or similar) is fine, except avoid spar varnish as it is designed not to get really hard. Ignore any "do not thin" advice on the can.

Bill

It so happens I have varnish and mineral spirits!

I had used good old Elmer's Glue-All to re-attach that one piece, but to finish the job, I was thinking of some techniques I've used for model rocketry. I prefer your idea, though, so going to run with it when the time comes. 

Thanks!

 - Robert


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#6 Jaz5833

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Posted 15 December 2020 - 11:45 PM

I have used this:

 

s-f500_main1_1.png

 

with great success to stabilize everything from rotten wood to cardboard.

 

It's incredibly thin and will follow a crack for several inches. So thin, you have to be careful or it will get everywhere. 


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#7 photomagica

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Posted 16 December 2020 - 12:52 AM

Jaz5833's suggestion of the cyanoacrylate stabilizer sounds good as well. I have not tired it. I'd recommend doing a test with any stuff you haven't used on some scrap material just to find out how it behaves and if it does the job you want.

Bill


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#8 The_Vagabond

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Posted 16 December 2020 - 12:17 PM

I have used this:

 

attachicon.gifs-f500_main1_1.png

 

with great success to stabilize everything from rotten wood to cardboard.

 

It's incredibly thin and will follow a crack for several inches. So thin, you have to be careful or it will get everywhere. 

I've used CA on my rockets before, for tube repairs. 

As Bill suggested, going to test it out. The entire front of the tube is de-laminating, so I have plenty of area to work with for tests. Meantime, I have picked up some new fittings, as well as securing a new mirror (needs to be trimmed, but I've worked with glass before, and even have the scars to prove it...).



#9 The_Vagabond

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Posted 16 December 2020 - 03:10 PM

I removed the mirror for closer examination. Some oxidation around the edges, plus one blemish, probably some something that hit the mirror. Shouldn't be too intrusive. I got lucky here. 

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  • SkyScope4.jpg

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#10 The_Vagabond

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Posted 16 December 2020 - 03:12 PM

The secondary is not salvageable. Fortunately, I have a spare, I just need to trim a little off to keep it from being too long. 

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#11 The_Vagabond

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Posted 16 December 2020 - 03:18 PM

Initial rebuild on the mirror cell. The new tension springs are probably going to need to be cut in half, as they are moving the mirror too far forward. This scope came with nuts instead of wingnuts for collimation. I added brass 6-32 wingnuts, resting on top of copper washers (which will add a little color contrast to all the brass). 

Not looking forward to some of the work that's coming (trimming the secondary), but that has to wait. Need to get other things done. 

But this telescope really speaks to me. 

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  • SkyScope6 - Edited (1).jpg

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#12 photomagica

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Posted 16 December 2020 - 03:43 PM

Consider protecting the shiny brass with a careful coat of clear lacquer spray. I like lacquer because any clear coating will eventually deteriorate. Lacquer can be removed easily with lacquer thinner. Then a bit of polishing, another coat and you are good for the next decade or two.

Bill


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#13 The_Vagabond

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Posted 16 December 2020 - 09:03 PM

Decided to approach the secondary mirror. While the eyepiece tube still needs to be painted, I wanted to get this done for testing. 
The telescope's secondary was in very poor shape. Luckily I had a similar sized mirror, though it was about 3/8" (almost 1 cm) too long. As for width, it is ever so slightly wider. However, lacking major shop tools, and only having a basic glass cutter at the moment, it is going to have to remain a touch wider, though I doubt it will be too much of a problem. 

(Also, I need to apologize for the following pictures. My poor somewhat smart-ish phone needs better lighting to perform well.)

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#14 The_Vagabond

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Posted 16 December 2020 - 09:04 PM

Not the clearest picture, but the cut ended up being ever so slightly crooked, due to the straightedge slipping. The card was going to be used as a backing to the mirror, but in the end wasn't needed. 

By the way, lest anyone think this was a second surface mirror, it's actually both. I foolishly sat it face down after snapping off the small section. 

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Edited by The_Vagabond, 16 December 2020 - 09:06 PM.

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#15 The_Vagabond

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Posted 16 December 2020 - 09:08 PM

I used contact cement to attach the new mirror to the secondary vane. 

Chances are good I'll brush paint the rest of the eyepiece tube assembly, as well as polishing up the brass section. 

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#16 The_Vagabond

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Posted 17 December 2020 - 02:13 PM

It took a couple of coats of urethane varnish and some glue, but the forward end of the OTA is in somewhat better condition. However, it has warped ever so slightly around the eyepiece holder (I hesitate to call it a focuser, as all it really does is hold the eyepiece). I will probably need to make a shim/disk for the eyepiece holder to shore everything up. This is where having circle cutters for cardstock comes in handy. 

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  • IMG_20201217_130608 (1) - Edited.jpg

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#17 The_Vagabond

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Posted 17 December 2020 - 02:25 PM

I decided to reassemble the OTA in order to test out the optics. Even though there is still much to do, I want to view the Jupiter/Saturn conjunction this evening. Besides, I am drawn like a moth to a flame to this lovely old telescope. 

Most of my astronomy these days is whitelight solar work, namely sunspot counts. I had a spare filter I had made for a now surplussed 76mm, so I broke it out and decided to view the Sun. It is apparent that the included eyepiece still needs some cleaning, and that the telescope needs to be better collimated. 

But the potential is there. 

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#18 DAVIDG

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Posted 17 December 2020 - 04:54 PM

  Having restored a number of these types of small aperture long focus Newtonians I recommend you test the secondary for how optically flat it is. Most of these small rectangular "flats" are just first surface mirrors and not precision optical flats. The  sharpness that these small aperture long focus mirror can produce if it has a smooth figure can be excellent but will be  hurt greatly with  a  poor quality diagonal. You will get  an OK image at low  to medium power with poor diagonal that can give you a false sense that the optics are OK but the sharpness will never be there at high power that these mirrors can produce. 

   Also you have to pay attention to the thickness of the diagonal  and the position of the mounting plate. On Criterion RV-4, the focuser with the diagonal stalk part of it, was manufacture wrong. The surface of the metal plate were the diagonal is mounted to,  is actually were the reflected surface of the diagonal should be. So the diagonal is mounted too far forward and to close the focuser. The result is that when the scope looks collimated the primary is tilted and you will always have astigmatism in the image and you'll never get good high magnification views So I would make a full scale  drawing of the were the surface is located in relationship to the mechanical axis of the focuser tube and the optical axis of the primary mirror to be sure the reflective surface of the diagonal is in the correct position.  I had to cut the mounting plate off  two  of the Criterion scope I restored and reposition them so the reflective surface of the diagonal was in the correct position. 

   Here are pictures of  a couple of the original diagonal in these types of small scope I have restored showing the poor optical quality.

 

                  - Dave 

 

bad diagonal.jpg

 

RV-4 diagonal.jpg


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#19 The_Vagabond

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Posted 17 December 2020 - 08:10 PM

  Having restored a number of these types of small aperture long focus Newtonians I recommend you test the secondary for how optically flat it is. Most of these small rectangular "flats" are just first surface mirrors and not precision optical flats. The  sharpness that these small aperture long focus mirror can produce if it has a smooth figure can be excellent but will be  hurt greatly with  a  poor quality diagonal. You will get  an OK image at low  to medium power with poor diagonal that can give you a false sense that the optics are OK but the sharpness will never be there at high power that these mirrors can produce. 

Hello David,

The replacement diagonal actually came out of a fairly recent (though inexpensive) diagonal that was damaged. Once it was cut to the correct length, it mounted rather easily on the stalk. But, we're still early into this project (right now, concerned about the fit and finish). The secondary is attached with a thin coat of contact cement, my preferred method, as it takes only a little work to remove them in the event things go awry. I certainly appreciate your advice! We'll see what happens next, hopefully this will suffice for now (holding my breath, at any rate). 
(EDIT - Also, at some point, I really need to invest in some optic flats)


Edited by The_Vagabond, 17 December 2020 - 08:18 PM.

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#20 The_Vagabond

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Posted 17 December 2020 - 08:16 PM

Before setting the SkyScope aside to do some more work on it, I decided to bring out the Harmonic Reed StarMaster and perform a comparison (not exactly side by side, as we are already pretty cold here). I had chosen two targets initially, the Pleiades and the Double Cluster in Perseus, but chose to go with the latter.
Through the SkyScope, the Double Cluster was a cloud of stars, though the eyepiece tube's shifting made things difficult from time to time. The clusters were bright, though, and rather impressive, considering I am still using its original eyepiece.
One thing I noticed about the StarMaster right away was the weight, or more to the point, its lack thereof. It is also shorter. While the OTA to the StarMaster is larger in diameter, the mirror is actually smaller, 3" (76.2mm) to the SkyScope's 3.5" (88.9mm).
Due to the StarMaster's tripod being shorter, aiming it at the Double Cluster was difficult, especially when one considers how high in altitude they are for me at this location at this time. Still, once they were located, the view was fairly nice. I have set aside the StarMaster's two eyepieces and am using a microscope eyepiece, a Ramsden, which gave a similar field of view to that in the SkyScope.
Cobbling together a couple of eyepieces for the SkyScope shouldn't be that difficult, and the same can be said for the StarMaster. What the StarMaster really needs, though, are longer, heavier legs. That simple change would make a big difference.

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#21 DAVIDG

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Posted 18 December 2020 - 12:29 PM

Hello David,

The replacement diagonal actually came out of a fairly recent (though inexpensive) diagonal that was damaged. Once it was cut to the correct length, it mounted rather easily on the stalk. But, we're still early into this project (right now, concerned about the fit and finish). The secondary is attached with a thin coat of contact cement, my preferred method, as it takes only a little work to remove them in the event things go awry. I certainly appreciate your advice! We'll see what happens next, hopefully this will suffice for now (holding my breath, at any rate). 
(EDIT - Also, at some point, I really need to invest in some optic flats)

 These scope can be elevated from being a "toy" to giving really sharp images if one pays attention to the optics a little bit. I would not take anything  for granted when it comes to the optics. As I said I have restored a number of scope like this and many scopes in general. People doing the restoration spend hours on the mechanics but make the mistake of believing there is nothing wrong with the optics. Unfortunately that is not the case and they are the most variable in quality of all the parts.  The big mistake restores make is to just look through the scope and if the image looks "good" to them they believe all is  fine. The problem  is 1/2 wave  or even worse optics will give an OK image that looks "good" too many at low to medium power or if the image looks to have issues, seeing, collimation, eyepiece quality etc are blamed vs the quality of the optics. A simple Foucault test will show if the mirror has errors and testing the quality of a diagonal against a known good one will show the quality of the diagonal.  

   These small aperture long focus Newtonians have the Law of Physics on their side. If the mirror is  a clean sphere and the diagonal optically flat to 1/8 wave or better, the over all wave front is a true 1/8 wave or better.  That is far better then most commercial scope and will give very sharp detailed images. 

    Here is  a link to my thread on restoring a late 50's Criterion Dynascope which is very similar to your SkyScope.

  https://www.cloudyni...rion-dynascope/

 

                   Happy Holidays 

 

                    - Dave  


Edited by DAVIDG, 18 December 2020 - 08:02 PM.

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#22 photomagica

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Posted 18 December 2020 - 01:56 PM

 These scope can be elevated from being a "toy" to giving really sharp images if one pays attention to the optics a little bit. I would not take anything  for granted when it comes to the optics. As I said I have restored a number of scope like this and many scopes in general. People doing the restoration spend hours on the mechanics but make the mistake of believing there is nothing wrong with the optics. Unfortunately that is not the case and they are the most variable in quality of all the parts.  The big mistake restores make is to just look through the scope and if the image looks "good" to them they believe all is  fine. The problem  is 1/2 wave  or even worse optics will give an OK image that looks "good" too many at low to medium power or if the image looks to have issues, seeing, collimation, eyepiece quality etc are blamed vs the quality of the optics. A simple Foucault test will show if the mirror has errors and testing the quality of a diagonal against a known good one with show the quality of the diagonal.  

   These small aperture long focus Newtonians have the Law of Physics on their side. If the mirror is  a clean sphere and the diagonal optically flat to 1/8 wave or better, the over all wave front is a true 1/8 wave or better.  That is far better then most commercial scope and will give very sharp detailed images. 

    Here is  a link to my thread on restoring a late 50's Criterion Dynascope which is very similar to your SkyScope.

  https://www.cloudyni...rion-dynascope/

 

                   Happy Holidays 

 

                    - Dave  

Dave,

Side bar conversation - what light source are you using to get the fringes when you test aluminized flats? I have trouble seeing the fringes when I'm testing aluminized items under fluorescent light.

I very much agree with you on optical quality. With a couple of my early telescopes I used a half-wave diagonal. When I changed that out for a 1/10 wave flat the improvement in image quality was remarkable.

Thanks,

Bill


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#23 The_Vagabond

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Posted 18 December 2020 - 05:02 PM

 These scope can be elevated from being a "toy" to giving really sharp images if one pays attention to the optics a little bit. I would not take anything  for granted when it comes to the optics. As I said I have restored a number of scope like this and many scopes in general. People doing the restoration spend hours on the mechanics but make the mistake of believing there is nothing wrong with the optics. Unfortunately that is not the case and they are the most variable in quality of all the parts.  The big mistake restores make is to just look through the scope and if the image looks "good" to them they believe all is  fine. The problem  is 1/2 wave  or even worse optics will give an OK image that looks "good" too many at low to medium power or if the image looks to have issues, seeing, collimation, eyepiece quality etc are blamed vs the quality of the optics. A simple Foucault test will show if the mirror has errors and testing the quality of a diagonal against a known good one with show the quality of the diagonal...

                   Happy Holidays 

 

                    - Dave  

I worked at a science center some years back and we had a veritable sea of RV-6's and a few RV-4's. I was rather fond of the 6's. The latter seldom got used, however. Impressive work on yours, by the way. Never had a chance to see what their stock performance was like. 

Right now, I'm working on simply trying to get the telescope back into presentable condition. I'm disabled, so cash is always tight, but I did order a couple of .75" minor axis diagonals for another project (ex-Meade, I believe). As I mentioned, popping that mirror off and replacing it shouldn't be too difficult when the time comes. The primary, though, has a little oxidation around the periphery.

When I remove the cell to work on the brass, I might very well conduct that Foucault test, as I certainly have the gear to cobble something of a test stand together. 

This has been a very tough year for me, and this telescope was supposed to be a simple, fun project. But I like the idea of turning it into an even more useful tool. Wasn't my original plan, as I have plenty of other telescopes. But seeing how far this narrow Newt can be pushed sounds like an interesting plan. 

Happy Holidays, 

 - Robert


Edited by The_Vagabond, 18 December 2020 - 09:01 PM.

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#24 DAVIDG

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Posted 18 December 2020 - 08:01 PM

Dave,

Side bar conversation - what light source are you using to get the fringes when you test aluminized flats? I have trouble seeing the fringes when I'm testing aluminized items under fluorescent light.

I very much agree with you on optical quality. With a couple of my early telescopes I used a half-wave diagonal. When I changed that out for a 1/10 wave flat the improvement in image quality was remarkable.

Thanks,

Bill

 Bill,

    It is  a monochrome mercury source made by Unilamp but that is not the reason the fringes are clearly visible when testing an aluminized flat. The reason they are easily seen is that I'm use a reference flat that  has a thin  transparent aluminum coating on it.  This better matches the reflectivity of the full aluminum coating on the flat your testing makes the fringes easily visible. 


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#25 photomagica

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Posted 19 December 2020 - 02:21 AM

 Bill,

    It is  a monochrome mercury source made by Unilamp but that is not the reason the fringes are clearly visible when testing an aluminized flat. The reason they are easily seen is that I'm use a reference flat that  has a thin  transparent aluminum coating on it.  This better matches the reflectivity of the full aluminum coating on the flat your testing makes the fringes easily visible. 

Thanks Dave - My flats have no coating, so I will try a better light source and see what happens. - Bill


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