Quote:
Originally Posted by Matt Wastell
[QUOTE What f ratio are you at when imaging?
Derek
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Hi Derek,
I have no idea regarding F ratios - someone once told me how to calculate but I have forgotten.
If you know reply and I will do my homework!!!!!!!![/QUOTE]
Hi Matt,
There is a most helpful article in the Projects & Articles section here on IIS, by Anthony Wesley "How to calculate focal length from plate scale"
http://www.iceinspace.com.au/63-386-0-0-1-0.html
If you do this then by dividing the the calculated focal length by the dia of your aperture you will get the your focal ratio.
Regards
Trevor