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A Question of Focal Length


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Hi all

I am planning to dip my toe in the dark world of lunar photography.  Before I plan a purchase of a camera I have a question.  I plan to use my f/5 Newtonian scope, should I Barlow it up to f/10 or f/15 for better results?

Thanks for any advice.

Paul

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you can if you want to but personally i would just drop ISO lower or raise SSPD higher . You should be able to make adjustments on your camera to suite your taste in exposures . My AT1010 , 80mm is f/6 , takes bright moon images unless i do adjustments as mentioned . 

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The optimum focal ratio for high res planetary imaging is dependant on the pixel size of your camera.

I’d aim for an f ratio of  about 5.3 x pixel size (in micron). So for a  ZWO 120 series with 3.75 micron pixels you want to be imaging at around f/20 and if you’re using the 178 series with 2.4 micron pixels you’re good at around f/13.

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