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Backfocus question c11& asi294

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#1 Nbsdsailor

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Posted 24 May 2019 - 12:14 AM

I'm new to AP. I'm looking at getting a oag and read that the celestron one is pretty good but I have to calculate backfocus because it's pretty long. I'd be using a C11 with a 6.3 reducer then the oag and then the asi294. Can anyone help me figure out what my backfocus would be? Or should I be looking at another oag?


Edited by Nbsdsailor, 24 May 2019 - 12:22 AM.


#2 gonnessia

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Posted 24 May 2019 - 12:41 AM

Would that be the reducer/corrector fot f/6.3 from Meade or from Celestron. These two have a different backfocus !

#3 Nbsdsailor

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Posted 24 May 2019 - 12:45 AM

It's the celestron one



#4 f300v10

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Posted 24 May 2019 - 04:01 PM

Nbsdsailor,

 

I happen to have the exact setup your describing, C11 with Celestron 0.63 reducer, Celestron OAG and ASI294MC Pro.  You need 105mm from the end of the reducer.  I the closest I could get with the spacers that came with the ASI was 108mm, which was using the 16mm M48/M42 + 11mm M42 ring on the ASI.  I swapped the 16mm for a shorter M48/M42 and am now at 105.


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