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Criterion DynaMax 8

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#51 DAVIDG

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Posted 22 August 2023 - 08:42 AM

I wonder if we could arrange to go through all of RP’s inventory and find the “good one”.

Chances are they’re all pretty similar in that they will vary considerably without any being particularly good.

 If so,  you would need a 8" or larger spherical mirror and a Foucault tester,  setup with Ronchi grating to test the correctors.  If you find the unicorn in the bunch, the secondary really needs  to be figured to remove the residue aberration of the system if you want a truly good system.

 

               - Dave  


Edited by DAVIDG, 22 August 2023 - 10:45 AM.

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#52 Gil V

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Posted 30 August 2023 - 07:36 AM

All we need to do now is find the unicorn.

Sounds like a fairy tale to me!
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#53 Goofyboy1

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Posted 01 September 2023 - 05:00 AM

Do you have any photos?

 

I'd test it out at low, medium and then high power before removing anything.

 

The corrector plus 2ndry can be removed and the corrector plate cleaned with acetone then soapy water, finally pure water. I doubt if there are any coatings on the plate, hopefully the mirrors are in good shape.

 

Most of the optics problems are usually due to the poorly made corrector plates which unfortunately can't feasibly be improved. It would be better to start from scratch but it's a really tough one.

 

David

Hello David,

 

Sorry for my late reply. I will upload tomorrow some photos. Do you have any request?



#54 Goofyboy1

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Posted 03 September 2023 - 05:20 AM

Here are some photos from the Criterion Dynamax 8” with Criterion RC-6 controller

 

 

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#55 Goofyboy1

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Posted 03 September 2023 - 05:22 AM

Next photos

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#56 Goofyboy1

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Posted 03 September 2023 - 05:25 AM

And next

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#57 Goofyboy1

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Posted 03 September 2023 - 05:27 AM

This two filters are stacked but can someone tell me what they are for??

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#58 Goofyboy1

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Posted 03 September 2023 - 05:31 AM

My big question is where and how too start cleaning everything and apply new lubricant?

 

I have distilled water and isopropyl alcohol (IPA / 2-PROPANOL) 98% 

 

 

I hope you can help me save this stuff and make the best out off it!

 

kind regards Joost 



#59 davidc135

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Posted 03 September 2023 - 05:34 PM

My big question is where and how too start cleaning everything and apply new lubricant?

 

I have distilled water and isopropyl alcohol (IPA / 2-PROPANOL) 98% 

 

 

I hope you can help me save this stuff and make the best out off it!

 

kind regards Joost 

Good luck with your project. My example is slightly later than yours, SN 4468. Unfortunately my experience is with optics rather than mechanics but hopefully others can give advice. GilV is the expert here.

 

David



#60 bobhen

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Posted 04 September 2023 - 10:36 AM

This two filters are stacked but can someone tell me what they are for??

I believe they are moon filters used to dim strong moonlight.

 

Bob



#61 Goofyboy1

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Posted 04 September 2023 - 11:03 AM

Thanks. It looks like they are the same. 



#62 bobhen

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Posted 05 September 2023 - 01:51 PM

Thanks. It looks like they are the same. 

"If" they fit together, then they are probably polarized, meaning that if you turn one the light throughput will change and you can make the view dimmer or brighter. 

 

Bob


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#63 Goofyboy1

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Posted 05 September 2023 - 11:53 PM

 I was at Stellafane this weekend and got 3 more Dx-8 correctors from  the person that bought out what was left of Criterion when they closed. I'm going to test them and maybe there is good one in this batch or one that won't take much to clean up, in my quest to have an optically excellent DX-8

 

                - Dave 

 

attachicon.gif dx8 correctors.jpg

Hello,

 

can you tell me what can be the difference between those correctors? I’m new and bought one and it need a good cleaning after years off not used by the finder. I bought it secondhand. 



#64 deSitter

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Posted 06 September 2023 - 12:32 AM

This two filters are stacked but can someone tell me what they are for??

That's probably a variable neutral density filter that works with crossed polarizers.

 

-drl



#65 Gil V

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Posted 06 September 2023 - 01:35 PM

My immediate concern with that scope is what looks like the separation of the rear cell from the tube. That can cause a bunch of trouble with alignment and collimation.


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#66 deSitter

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Posted 06 September 2023 - 03:32 PM

My immediate concern with that scope is what looks like the separation of the rear cell from the tube. That can cause a bunch of trouble with alignment and collimation.

Look in the bright side, the most difficult part of an overhaul is already done!

 

-drl



#67 Goofyboy1

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Posted 07 September 2023 - 12:44 PM

My immediate concern with that scope is what looks like the separation of the rear cell from the tube. That can cause a bunch of trouble with alignment and collimation.

What will be the best way too hold the tube on his place? Clue or screw it?

 

the optics and oculars where so dirty that it took me a dag to clean it all



#68 Goofyboy1

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Posted 07 September 2023 - 12:47 PM

Look in the bright side, the most difficult part of an overhaul is already done!

 

-drl

In the future I need too paint is but for now it’s Oke. 



#69 Gil V

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Posted 11 September 2023 - 03:22 PM

It depends. Can you see the gap between the rear cell and tube change when you tug on the front of the scope? If not, leave it alone and try it out. It's a major repair. 

 

If the telescope doesn't hold collimation, it's unavoidable. 


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#70 Gil V

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Posted 11 September 2023 - 03:24 PM

It is possible I built part of that scope personally, based on serial number and color configuration. I'll give you (my) lifetime warranty support.


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#71 Goofyboy1

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Posted 15 September 2023 - 02:06 PM

Hi,

 

thanks!

 

bit in your opinion is the best way too fix the tube on the mirror frame? I have peeled off silicone but I think that isn’t from the factory.



#72 Goofyboy1

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Posted 15 September 2023 - 02:08 PM

Btw I can pull off the tube from the cell



#73 deSitter

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Posted 15 September 2023 - 02:11 PM

Btw I can pull off the tube from the cell

Since the alignment of the corrector depends on the tube being accurately parallel to the optical axis, you should collimate it with the tube pushed as far as possible onto the back cell, so that it will be collimated again when it comes time to secure it.

 

-drl



#74 Goofyboy1

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Posted 15 September 2023 - 02:30 PM

I know but what is better clueing it or screwing it too the cell?



#75 deSitter

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Posted 15 September 2023 - 02:42 PM

I know but what is better clueing it or screwing it too the cell?

No opinion, no experience, others will know. But the collimation part is essential.

 

-drl




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