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Which size filters? (31 or 36mm) for ASI294MM and is a focal reducer/flattener required for SCT?

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#1 ryanha

ryanha

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Posted 23 September 2020 - 02:33 PM

I just put in an order for a ZWO ASI294MM with a Celestron OAG + ZWO174 guide camera.

 

(ngl, I'm a bit nauseous about how much $$ I just spent smile.gif)  

 

Anyway, I will be putting this beautiful equipment on a Celestron SCT 8".

 

My question is:

1.) should I go for 31 or 36mm filters & filter wheel (planning on doing 7 position)

2.) Is a focal reducer/flattener required or can I go with this setup to start with?

 

FWIW, I think I will likely eventually one day get another telescope (shorter FL and faster optics) so ideally I get filters that will carry over if that makes a difference.

 

Thanks in advance!  And if you don't mind (even if you don't think it) tell me I made some good choices just now about spending this much money to get poor nights sleep smile.gif

 

--Ryan


Edited by ryanha, 23 September 2020 - 02:34 PM.


#2 glancey

glancey

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Posted 23 September 2020 - 02:55 PM

I have the ASI294 color that I use on a Celestron SCT 8. A focal reducer/flattener is a must-have for DSO imaging. I have both a Celestron .63 and a NightOwl .4. These reduce the imaging time by a significant factor. Hyperstar is another, more expensive option for fast imaging. The 294 works great for DSOs.

 

For planetary imaging, a barlow lens is needed to increase the focal ratio to match the 4.63um pixel size of the ASI294. A rough estimate of the correct ratio is 5 * pixel size. I have a Celestron 2.5X barlow that I use to acceptable effect for planetary imaging. I really should get either a 1.5X or 2X barlow for better imaging, or a camera with a smaller pixel size for planetary work. 

 

Sorry I can't help you with the filters.


Edited by glancey, 23 September 2020 - 02:58 PM.



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