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View Full Version here: : Focal ratio myths


Geoff45
14-01-2010, 09:11 PM
Are the following assertions true or false?


The smaller the f number, the shorter the exposure you can use.
A 10" f8 scope is slower than a 6" f4 ie needs longer exposures
Aperture is more important than focal ratio

Interesting reads here
http://www.stanmooreastro.com/SamplingFratioMyth.htm
http://www.stark-labs.com/blog/files/FratioAperture.php

Geoff

deadsimple
15-01-2010, 01:42 AM
The second link was especially interesting, thanks for posting.