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Criterion Dynascope 6 restoration

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6 replies to this topic

#1 Wjeremy 15

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Posted 21 May 2024 - 02:07 PM

Recently our club received a donation of this 6 inch f/8 criterion Dynascope. It fell to me to pick it up and test it. The scope collimated easily and I was impressed by the star test, at least as good as my modern xt8 and perhaps better. It also came with most of the original components, including the focuser, rings for the finder scope( although not the finder scope itself), clock drive, and original base, which is quite heavy.

The mirror performance has made me want to restore this telescope, I think it could be a really nice visual instrument for someone.

However, the 1.25 in focuser is quite tarnished, wobbles slightly, And has to be held at focus when using a heavier eyepiece else it slips. Also the base, while very sturdy, is unwieldy and also quite tarnished and would require some effort restore.

I am torn torn about how to spruce up this scope. Part of me wants to buy a modern focuser and finder, add a dovetail plate, and put it on a modern mount. It would certainly be a pleasure to use that way. But I think there is some value in restoring the old as much as possible. For one thing, it's just interesting to see how things were designed and how they differ from modern instruments. Something is lost if I just replace all those pieces that are slightly inconvenient for not quite as good.

No doubt this dilemma is faced all the time, but I'm just curious what other people's thoughts are.

#2 Augustus

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Posted 21 May 2024 - 02:18 PM

I did a full tear down of one of these once, I've owned 8 of them. Here are my thoughts:

  • OTA is best painted at an auto body shop, the paint tends to yellow/stain.
  • Can use drill-mounted buffing wheel on focuser drawtube, CW shaft, setting circles
  • Fairly easy to repaint GEM/pier

If you really hate the focuser a Moonlite or something like that could be retrofitted on there, but the 1.3" secondary won't illuminate a 2" eyepiece very well

 

Before/after of the OTA, I'm missing pics of the mount pre-restoration

 

IMG_9504s.jpg

 

IMG_9945s.jpg

 

The spring-loaded clock drive is awesome on these, IMO probably the easiest GEM to use and a very Dob-like experience. Fix it up and keep it on the original GEM. If you want a Dob, sell it and buy one.


Edited by Augustus, 21 May 2024 - 02:19 PM.

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#3 Garyth64

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Posted 21 May 2024 - 02:20 PM

I would try and keep the scope as original as possible, especially if it is an older one

 

Do you know the approximate year it was made?  Is it a white tube, or a grey crinkle finish? Does it have rotating rings?

 

Can you take some pictures?

 

This is what mine would look like if I had the original mount:

 

file photo 04a.jpg

 

It's from about 1958.

 

If you're scope is like that, I have extra original 50mm finder that I can give you.

 

EDIT: The original focuser works just fine,  it probably just needs new shimage, and adjustment.

 

Criterion 04.jpg


Edited by Garyth64, 21 May 2024 - 06:23 PM.

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#4 rachnoman

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Posted 21 May 2024 - 03:01 PM

If anything, I'd jettison the original focuser and replace it with a superior 1.25" focuser. 


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#5 Wjeremy 15

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Posted 21 May 2024 - 07:20 PM

Thanks for the comments.

 

Pics below.

 

PXL 20240521 233843968.MP
 
PXL 20240521 233916900.MP
 
PXL 20240521 233928397.MP

 

I am inclined to leave it as original as possible, so appreciate the restoration tips.

 

Not sure how to get access to a body shop for this kind of project.  I was thinking remove hardware, careful taping and gloss spray paint.  Is that crazy?  My painting knowledge is....thin

 

Not sure of the year.  

 

Garyth, if the guide scope looks like the right one based on my pictures I'd love to buy it from you 


Edited by Wjeremy 15, 21 May 2024 - 07:20 PM.


#6 Augustus

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Posted 21 May 2024 - 07:43 PM

Thanks for the comments.

 

Pics below.

 

 
 
 
 
 

 

I am inclined to leave it as original as possible, so appreciate the restoration tips.

 

Not sure how to get access to a body shop for this kind of project.  I was thinking remove hardware, careful taping and gloss spray paint.  Is that crazy?  My painting knowledge is....thin

 

Not sure of the year.  

 

Garyth, if the guide scope looks like the right one based on my pictures I'd love to buy it from you 

Not sure what is up with the S/N but that's an early unit, not too many of them have setting circles



#7 Garyth64

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Posted 21 May 2024 - 08:44 PM

The finder I mentioned will not fit into your brackets, it is a 8x50mm finder.

 

But, I do have an original 6x30mm finder that will fit those brackets.  The paint was badly scratched, and I sanded, primed, and repainted it.  It still says Criterion on the tube, but it is hard to see.

 

If you would like it, you can have it for the shipping cost.

 

EDIT:  The finder is in excellent condition, but the glue between the lenses of the doublet is failing. Not really a problem.


Edited by Garyth64, 21 May 2024 - 09:22 PM.

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