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Criterion Dynascope 12 saved from doom!

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#51 Jason H.

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Posted 10 May 2020 - 11:12 AM

No markings or etching pen marks anywhere on the glass, only this masking tape with 72" written on it.

 

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#52 Jason H.

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Posted 10 May 2020 - 11:14 AM

12.5" diameter

 

smDSC00647.jpg


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#53 Jason H.

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Posted 10 May 2020 - 11:15 AM

2" thick

smDSC00624.jpg



#54 Jason H.

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Posted 10 May 2020 - 11:18 AM

Collimation springs and green felt in good shape.

 

smDSC00629.jpg



#55 DAVIDG

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Posted 10 May 2020 - 11:34 AM

 I would just wire brush the focuser  or any cast iron part,  then a light coat of primer then wrinkle black paint on any part that used that finished. 

   You mentioned wrinkled green ?  If you are referring to the tube as  looking  green it should be wrinkle gray and may have faded.  I have a scope with that finish and have seen many with the same gray wrinkled finished  but never green. 

   If you need to repair area of paint loss on the tube, I would spray wrinkle white over those area since I don't think you can get the wrinkle gray any more, then respray the whole tube with a light coat of gray as to not fill in the wrinkle texture.

   As for any aluminium parts,  just use steel wool to shine them back up and spray clear enamel over them so they will never oxidize again.

   The  mirror coating  is very usable, just give it a good bath. As I said before have it and the diagonal tested before you spend  a couple hundred dollars having them recoated. I have seen many of these large Newtonians were optics have had issues and as the other poster stated the results of when he tested one of these mirrors from the same scope wasn't that good either.Don't let a "good" image of the Moon fool you that you have no problem with your optics. Optics that are 1/2 wave will give an image like that. As the other poster stated, the Criterion he tested was used for many years and people thought it was fine.

 

               - Dave 


Edited by DAVIDG, 11 May 2020 - 08:28 AM.

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#56 Jason H.

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Posted 10 May 2020 - 02:58 PM

Thanks Dave for the tips!  On the color, whatever the color is in the image below :^), and regarding the optics, since I don't know anybody, and I don't want to ship this anywhere, to me the best test I probably could do is to pull it all back together, collimate, and try to get some diffraction rings in and out of focus?  Although I can tell the secondary is going to need a re-coating (and there might be too much coating-induced light dispersion on the primary for it to also need a re-coating?) my understanding is that these secondary flats may have been from Japan, and the primary's were made in Criterion's optics lab and the coatings were sub-contracted to third parties?  Regarding the Japanese flat (if it is one), since I highly regard the Japanese amazing skills, I'm going to trust (take a chance) that the figure of that flat isn't going to be a problem (but I'll focus on that if the collimation test doesn't work out).  And with regard to the other stuff that came out of the Criterion optics lab (at least as far as small newtonians are concerned), I've been very lucky so far with that, so when it comes down to it, if I can't get good concentric diffraction rings (I'm a semi-retired planet imager who experimented with cheap gear, hoping to do it again this coming Planet Season), then the optics aren't good enough (i.e. without circular concentric diffraction rings, it'll have to be re-figured IMO).  I see that Spectrum Coatings  is very nearby me over in Deltona (1/2 hour drive), does anybody know how good they are? (man that would be extremely lucky if I could drive them over there! :^)     

 

sm3DSC00560.jpg

 

 

 

 I would just wire brush the focuser  or any cast iron part,  then a light coat of primer then wrinkle black paint on any part that used that finished. 

   You mentioned wrinkled green ?  If you are referring to the tube as  looking  green it should be wrinkle gray and may have faded.  I have a scope with that finish and have seen many with the same gray wrinkled finished  but never green. 

   If you need to repair area of paint loss on the tube, I would spray wrinkle white over those area since I don't think you can get the wrinkle gray any more, then respray the whole tube with a light coat of gray as to not fill in the wrinkle texture.

   As for any aluminium parts,  just use steel wool to shine them back up and spray clear enamel over them so they will never oxides again.

   The  mirror coating  is very usable, just give it a good bath. As I said before have it and the diagonal tested before you spend  a couple hundred dollars having them recoated. I have seen many of these large Newtonians were optics have had issues and as the other poster stated the results of when he tested one of these mirrors from the same scope wasn't that good either.Don't let a "good" image of the Moon fool you that you have no problem with your optics. Optics that are 1/2 wave will give an image like that. As the other poster stated, the Criterion he tested was used for many years and people thought it was fine.

 

               - Dave 

 


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#57 DAVIDG

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Posted 10 May 2020 - 03:24 PM

 The finder and tube looks to be the wrinkled gray.  Just found out the VHT also now makes wrinkled gray https://www.ebay.com...AiABEgLCUfD_BwE

   So you can repaint the finder. The finder bracket I'm, sure you can tell was once wrinkled black.  Looking for concentric diffraction circle is not test for spherical aberration only collimation and astigmatism. I'll post later how to correctly do a star test to determine the spherical correction.  Unfortunately I have benched tested around 50 RV-6 mirrors over the years include the one from my own 1976 RV-6 that bought new and all have been  uncorrected. I have tested around 12, RV-8 mirrors and they all have been spheres instead of parabolas so very much undercorrected. Unfortunately owners of these scope think the optics are great until they look through a telescope with true 1/8 wave optics then they see what they have been missing.  Again I'll point to the other 12" mentioned were for 50 years the owner thought the scope gave good images. Unfortunately for all that time they missed out what good optics will show.

 

           - Dave  


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#58 Jason H.

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Posted 10 May 2020 - 03:38 PM

Thanks Dave very much for that info!  And as I mentioned, although I've been somewhat semi-retired from planet imaging, because the images being posted over in Solar System imaging got so amazing after 2014, I didn't see much point of posting any more my modest point-n-shoot camera images afocal at the eyepiece of the Criterion 6 and 8 (my best-of afocal images mosaic up to 2014 is below, most of the planets in the RV-8, and the Moon and a couple other things in the RV-6, and one comet camera only), especially because the new ASI cameras that came out were amazingly better, but also because of the incredible difficulty of taming the Criterion clock drives at such high magnifications (it was a physical workout to say the least).  Since then I have made some significant improvements to the tuning of those clock drives where they are much more precisely tracking now, but I felt I really needed a big improvement here image scale and resolution-wise before contemplating ever posting again in Solar System Imaging.  I had been somewhat hopeful that this 12" telescope would fit that bill without re-figuring because I hadn't heard of any problems from these until now, my fingers are crossed (but with an un-signed mirror one has to go "hmmmm", but I'll definitely pass along the outcome of where these optics are now and if they'll need a major re-figuring or not (at least with regard to diffraction rings and planet images).  If they do I'll probably have it done eventually, but I don't have a clue who is doing these things well these days, and I'm pretty sure I would make it worse if I tried :^) So researching that would be a coming objective.  

 

EDIT - here at this link  https://floridaastro...stro-jason.html    you can see some of my other Criterion image experiments and even how things looked in real-time in the videos. 

 

BestAfocalMontageByJasonHigleySept2014-UrAdd.jpg


Edited by Jason H., 10 May 2020 - 07:09 PM.

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#59 rcwolpert

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Posted 10 May 2020 - 04:10 PM

It’s quite easy to ship out a 12” mirror. I had a 12.5”x2” mirror that I shipped out twice with the secondary with no problems. This would be the perfect time to ship it out for testing, refiguring (if necessary), and recoating, all while you work on restoring everything else. You have one amazing scope there, and that size mirror with 1/8 wave optics gives super views. I sure do miss my 12.5” f/6.3 with specially selected Coulter mirror.  Anyway, this is a fun topic to follow!


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#60 Starsareus

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Posted 10 May 2020 - 07:34 PM

Good for you! Last time I saw a 12" was in their Church Street (factory floor) back in the late 50s!  My 2 cents here. I restored maybe 16 RV-6 Scopes & none were bad. One concern is it may be under mounted (no easy fix). I am re storing one 8" Deluxe now, one more to do and 2  6" Deluxe scopes to follow.  I am a Criterion fan.  I prefer VHT Spray now over Rustoleum/Krylon, due to issues with clogging etc. In past those two were good resources. They never came in Green, but the original gray wrinkle changed over the many years. I visited the paint shop that painted these, but sadly now an automotive "chop shop". Dave's update on VHT Gray will be tried.(Thanks Dave).

 

I use WERA branded screwdrivers on many scope projects, especially where screw slots are questionable. They grab when others will not. Less of a chance of the screwdriver going through the main tube or your hand, due to Laser modded tips.  Personally, I apply a little "P B Blaster" on screws that will be removed, but first let it stay on a day.  Rust I use either Evaporust (Good on your classic sportscar) or Telescope. Also use white Vinegar ! Buy at Walmart etc. by the gallon (cheaper) and what you don't use, put on your salad!


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#61 clamchip

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Posted 10 May 2020 - 07:56 PM

Something interesting about wrinkle gray is back when you could still buy it 

I over baked it a little, not much, but it came out of the oven slightly green.

You can see the two parts I painted, the saddle and the counterweight.

Robert

 

post-50896-0-26802000-1421942838_thumb.jpg

post-50896-0-73996400-1421942802_thumb.jpg

post-50896-0-12685700-1421972265_thumb.jpg


Edited by clamchip, 10 May 2020 - 07:59 PM.

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#62 Terra Nova

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Posted 10 May 2020 - 10:23 PM

I'm so glad that you finally found the scope you have been looking for for so long. Congratulations. I hope you can get the guy to give you the mount that goes with it. When you finish you'll have an amazing instrument l have a friend in Cincinnati that has the 10" Dynascope Deluxe, all original as he purchased it nearly fifty years ago. It's the one with the mount on the bell pedestal with the short wooden tripod inside, and the 'chrome fenders' with Dynascope etched in cursive. It's remained inside when not in use and it still looks new. I always said, if Cadillac had made telescopes back in the day, they would have been Dynascopes! Keep us posted. It's a fascinating project you have there.


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#63 DAVIDG

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Posted 11 May 2020 - 09:34 AM

 Here is how you do the star test correctly. This is how the optics are judged at Stellafane and  a couple of  the judges made the optics that fixed the Hubble and optics on the New Horizon mission to Pluto.

    Most amateurs do the test wrong which leads to them thinking they have great optics. First you are looking at the defocused image of a medium to bright star. A star that is in focus doesn't show the defects in the wavefront. Next you need to use an eyepiece that has a focal length close to  or equal to the F-ratio of the scope. So if the scope is f/8 then you need 8mm eyepiece or close to it. This gives the correct magnification to see the diffraction pattern clearly.  Now you center the star in the eyepiece and bring it to focus. Next you defocus  inward only by a SMALL amount as in a 1/16 of turn of the focuser. You should see the defocused image break up into  a diffraction pattern of rings and with a black circle in the middle. The black circle is the shadow of the secondary on the Newtonian or Cassegrain. Note the size of the defocused image,  the size and brightness of each ring in the pattern and size of the shadow of secondary in the middle of the pattern. Now goes back to focus and defocus  outward by exactly the same amount inward. So the OD of the defocused image should be the same as the inward image. Again note the size and brightness of the diffraction rings  and the size of the black circle in the middle which is again the shadow of the secondary. 

    See my chart. If the black circle ( shadow of the secondary)  is bigger on the inside of focus then the outside then the optics are undercorrected.  If the black circle is smaller on the inside of focus then the outside then they are  over corrected. If they are the same size the optics are well corrected. The diffraction pattern should look the same. If the shadows are the same but the rings have different size and brights then you have zones especially the outer ring.  If it is sharp on one side and "hairy" on the other then you have a  turned edge.  

You can have a condition were you see no  black circle on one side but a large one on other. That is badly corrected optics and unfortunately I see that many times.

   Again let me stress that you need to defocus only by a small amount and by the same amount of each side of focus. You can easily make the pattern look the same or very similar by defocusing by different amounts and give a false positive results. 

 

 

                             - Dave 

 

STAR TESTING.jpg


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#64 Jason H.

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Posted 11 May 2020 - 10:22 AM

Thanks Dave, this is very helpful, and I'm sure this would be a great reference to everyone lucky enough to come across your post (I know I'll be using it as a local screen capture from now on.)  I had seen similar writings over time (in long lost paper versions and online references), but not as concise and all in one view/screen length.  I can't wait to bring it together soon as-is to see what's going on.

 

Clear skies and good seeing, Jason H.



#65 Jason H.

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Posted 11 May 2020 - 10:28 AM

Is there an all-in-one re-figure/re-coating shop you'd recommend?  Perhaps one that guarantee's 1/8th wave? (or better :^)

 

 

Jason H.

It’s quite easy to ship out a 12” mirror. I had a 12.5”x2” mirror that I shipped out twice with the secondary with no problems. This would be the perfect time to ship it out for testing, refiguring (if necessary), and recoating, all while you work on restoring everything else. You have one amazing scope there, and that size mirror with 1/8 wave optics gives super views. I sure do miss my 12.5” f/6.3 with specially selected Coulter mirror.  Anyway, this is a fun topic to follow!


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#66 Jason H.

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Posted 11 May 2020 - 10:33 AM

It is a great honor that you have posted here! (especially with only 163 posts since 2008) and apparently great experience since at least the 1950's, and very on-point valuable tips; thanks!

 

Jason H.  

Good for you! Last time I saw a 12" was in their Church Street (factory floor) back in the late 50s!  My 2 cents here. I restored maybe 16 RV-6 Scopes & none were bad. One concern is it may be under mounted (no easy fix). I am re storing one 8" Deluxe now, one more to do and 2  6" Deluxe scopes to follow.  I am a Criterion fan.  I prefer VHT Spray now over Rustoleum/Krylon, due to issues with clogging etc. In past those two were good resources. They never came in Green, but the original gray wrinkle changed over the many years. I visited the paint shop that painted these, but sadly now an automotive "chop shop". Dave's update on VHT Gray will be tried.(Thanks Dave).

 

I use WERA branded screwdrivers on many scope projects, especially where screw slots are questionable. They grab when others will not. Less of a chance of the screwdriver going through the main tube or your hand, due to Laser modded tips.  Personally, I apply a little "P B Blaster" on screws that will be removed, but first let it stay on a day.  Rust I use either Evaporust (Good on your classic sportscar) or Telescope. Also use white Vinegar ! Buy at Walmart etc. by the gallon (cheaper) and what you don't use, put on your salad!


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#67 Jason H.

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Posted 11 May 2020 - 10:41 AM

Hi Robert, how do these get "baked"?  Fumes toxic I'd imagine? Baking makes them ceramic-like/tough/indelible/impact resistant? That Zynolyte is apparently from the '70's, is there a modern equivalent bake-able product?

 

Jason H.

Something interesting about wrinkle gray is back when you could still buy it 

I over baked it a little, not much, but it came out of the oven slightly green.

You can see the two parts I painted, the saddle and the counterweight.

Robert

 



#68 rcwolpert

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Posted 11 May 2020 - 01:08 PM

Is there an all-in-one re-figure/re-coating shop you'd recommend?  Perhaps one that guarantee's 1/8th wave? (or better :^)

 

 

Jason H.

Yes, there are, but it's been many years since I've had my mirror done, and I don't even know if the people I used are still in business. Dave would know the best place to send your mirror.  Dave . . .?



#69 clamchip

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Posted 11 May 2020 - 08:26 PM

Hi Robert, how do these get "baked"?  Fumes toxic I'd imagine? Baking makes them ceramic-like/tough/indelible/impact resistant? That Zynolyte is apparently from the '70's, is there a modern equivalent bake-able product?

 

Jason H.

To cure or dry the paint you can speed up the process by baking the parts in the oven.

If I remember correctly about 200degF for a half hour or so.

Otherwise the wrinkle paints take a long time to fully harden, and this applies to modern

wrinkle paints.

You will know it's happening in the Kitchen, it's the oil base in the paint.

If you've ever cooked Spam on the stove top it's a kissing cousin.

One of my favorites is to pan fry Teriyaki Spam diced into cubes 'till brown, this is where it 

will smoke up the kitchen a little. Toss in some broccoli, serve on rice.

You can mask your paint bake with the Spam cook, if you need to. 

 

Robert 


Edited by clamchip, 11 May 2020 - 08:35 PM.

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#70 Jason H.

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Posted 11 May 2020 - 10:11 PM

The mount!  Is it heavy?  It is one teaspoon shy of collapsing into a neutron star, add the tube and it'll go all the way to a singularity :^)  I have no idea how heavy it actually is, but moving it myself was a challenge (in two pieces), and marrying them together alone was pretty scary too (I switched from sneakers to sandals when I got home :^), in retrospect, I won't be around this thing without shoes on again)  and I was genuinely concerned about possibly losing a toe a couple of times, or it tilting over and taking out my garage door (I think it could actually do that if not careful).

Attached Thumbnails

  • smDSC00657.jpg

Edited by Jason H., 11 May 2020 - 10:38 PM.

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#71 Jason H.

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Posted 11 May 2020 - 10:16 PM

"CRITERION 31"      I don't know what the 31 is for.

 

smDSC00660.jpg


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#72 Jason H.

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Posted 11 May 2020 - 10:23 PM

Serial number "1590" matches the one on the telescope tube.  All of the text on the metal tag reads

DYNASCOPE MODEL
SERIAL NO.
1590
MANUFACTURED BY
CRITERION MFG. CO. HARTFORD, CONN.
U.S.A.
TRADEMARK REGISTERED U.S. PATENT OFFICE

 

 

smDSC00662.jpg


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#73 Jason H.

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Posted 11 May 2020 - 10:28 PM

At some point getting into this box will be interesting I think, I'll take photos when I eventually get in there.

 

smDSC00654.jpg


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#74 Jason H.

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Posted 11 May 2020 - 10:34 PM

I don't know what this is yet on the other axis.  Eventually Looking inside that box will be even more fun!

 

smDSC00655.jpg


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#75 Jason H.

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Posted 11 May 2020 - 10:41 PM

That box in context.

 

smDSC00661.jpg


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