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Which Focal Reducer?

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OK, so my first attempts at imaging have been not so great. I am looking to get a focal reducer for my 6" SCT F10 1500mm and cant decide if i get 3.3 (F3.3 495mm) or 6.3 (F6.3 945mm)

I have seen people making masks but i think ill end up just buying one... then ill have to work on my alignment some more i guess..

anyone used a focal reducer on a SCT of this size? any possible problems with going as low as 3.3?



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Yes the 3.3 is a horror dating back to webcam sized chips in the early CCD days. Keep away! If it were as easy as that to create an f3.3 imaging rig you wouldn't see all those little apos out there imaging away.

SCT imaging is difficult. An aftermarket Crayford is also a good idea but all these add ons add up. The long focal length will require accurate tracking, which means good autoguider, good balance and good polar alignment.


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f/3.3 reducer is for CCDs smaller than 2/3" (2/3" is max). f/6.3 provides imaging circle for APS-C sized sensors (DSLR and others). For guiding - OAG will be most effiecient (as you are using quite big focal length). I used Celestron Radial Guider with C8 at f/10 and f/6.3 and now I'll try to use that with C11 :)

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