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Request for assistance and/or clarification:

Celestron EAA astrophotography equipment beginner accessories
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#1 SWHasson

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Posted 16 May 2019 - 02:10 PM

Hello everyone,

 

I am looking to get started with EAA and astrophotography and have a few questions about equipment and setup.  I have a Celestron 800 EdgeHD with a 0.7 focal reducer on a CGEM II mount.  I am considering a ZWO ASI294MC-Pro as the main camera and a ZWO ASI 290MM-mini as the guide camera.  Both of these would be connected to the focal reducer using the ZWO OAG.  Software wise either the ZWO ASIAir or SharpCap.  Post processing will be decided later.

My questions/confusions come from the required back focus for this setup.  I have read on the forum that Celestron requires a 105mm back focus when using the focal reducer.  I have also read that you can’t use the Celestron OAG for this as it is too large and extends past the required back focus.  ZWO literature indicates a 55mm back focus.  ZWO also offers diagrams of configurations to achieve this but I am unsure of what I am trying to reach:  105mm or 55mm?

 

Once the back focus is determined, what equipment will be required to achieve it?  I know that some of the components are included with the cameras and OAG mentioned.

Any assistance would be greatly appreciated.

Thank you in advance.

 

Scott.



#2 premk19

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Posted 16 May 2019 - 02:16 PM

Scott,

ZWO offers suggestions for achieving 55mm backfocus because that's commonly used for many refractor flatteners and reducers. The 8" EdgeHD reducer requires 105mm - you can get 55mm using zwo's method, and I believe the Celestron T-adapter fills the remaining 50mm (after removing the 28mm extension)

 

https://www.celestro...dapter-edgehd-8


Edited by premk19, 16 May 2019 - 02:21 PM.


#3 f300v10

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Posted 16 May 2019 - 02:59 PM

Scott,

 

I'm using the same ZWO cameras you listed with a C11 (non-edge) and the 0.63 Celestron reducer/corrector along with the Celestron OAG without issue.  The 0.63 reducer has the same 105mm backfocus requirement as your .7 Edge, so what works for me will also work for you.

 

A set of M48 extension tubes will help you get close to the spacing you need.  I have these and they work well for the price:

 

https://www.amazon.c...0?ie=UTF8&psc=1

 

 

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#4 SWHasson

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Posted 16 May 2019 - 05:32 PM

Thank you for the insight and recommendations.  Back to the planning board again.

 

Clear skies!

 

Scott.




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