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RC Secondary Electronic Focuser - how does it integrate?

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#1 Dodde

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Posted 05 August 2020 - 01:50 AM

Saw that RainbowAstro offers a secondary mirror focuser for GSO/clones in the 8-12" ranges. Somehow I cant get a grasp on how this thing integrates into the function of the OTA other than that it can shift the secondary in/out to focus I assume.

 

1) Do you still need the primary focuser at all, i e is it perhaps possible to use adapters/extender rings to reach a rough back focus distance and then rely on the secondary focuser for focusing only?

2) Does using this type of focuser mitigate any of the notorius issues with the focuser/mirror cell of the GSO RC type scopes?


Edited by Dodde, 05 August 2020 - 01:51 AM.


#2 MikiSJ

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Posted 05 August 2020 - 02:44 AM

In the early '80s I had a custom 14.25" custom cass made for me. It had a terrible focuser so I decided to make a secondary mirror focuser.

 

I ordered some parts from a catalog (no internet back then) and with the help of my drill press, I made a focuser that worked really well.

 

To answer your question about the original focuser - I never used the one that came with the OTA.



#3 Dodde

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Posted 06 August 2020 - 12:33 PM

To answer your question about the original focuser - I never used the one that came with the OTA.

Ok.

 

What did you put at the back of your scope then? Another focuser? Extension rings? Another focuser? What was your focusing routine?



#4 MikiSJ

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Posted 07 August 2020 - 12:44 AM

I used the original focuser to hold the eyepiece/diagonal to get an initial focus position and I then locked the original focuser down so it would move. The secondary focuser I cobbled together, was operated rack and pinion fashion with a 12v DC motor and a reversing switch in a handheld assembly.

 

There was very little lateral motion of the secondary and it was easy to get the various eyepieces I used (all non-parfocal) to focus.

 

I was actually quite pleased with myself for designing and fabricating the secondary focuser into my kit.




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