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Older Celestron 1.25” visual backs

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#1 russell23

russell23

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Posted 01 June 2020 - 09:58 PM

I recently picked up an older Celestron 80mm f/11.4 achromat with 1.25” focuser.

 

Problem #1: My only 1.25” star diagonal is one of those old prisms from the 80’s that you have to slap this way and that until you get it into collimation.

 

Solution to problem #1: I buy a Williams optics 1.25” carbon fiber 1/12th wave mirror diagonal. 
 

New Problem #2: The WO diagonal has a tapered barrel that is not captured tightly with the focuser set screw.

Solution to problem #2 attempt #1: I place a Blue fireball 1.25” 1” extension tube with compression ring in the focuser and the diagonal into the extension tube.  
 

    Problem 2b: The blue fireball compression ring does not secure the diagonal without some shift.

 

Solution to problem 2b:  Back the diagonal out to the straight part of the diagonal nose piece.

 

     Diagonal now secure.

 

Problem #3:  Whatever part of me that is OCD hates this solution and has to believe there is a better solution that still involves the Optically excellent Williams optics diagonal.  
 

Question: What are the threads I’m working with on the visual back of this 1.25” focuser? Are the male threads T threads?  If so, Blue fireball makes an adapter that would work assuming I don’t run into the same issue I did with the 1” blue fireball extension tube.
 

What are the female threads in the focuser draw tube?
 

Or should I stop worrying about it and stick with the problem 2b solution?

 

Pictures of visual back and focuser:

Attached Thumbnails

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Edited by russell23, 01 June 2020 - 10:02 PM.



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