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Hi Martin, just square the aperture in inches to get the light gathering ability
relative to a different size scope. 3"x3=9, 4"x4=16, 6"x6=36, 8"x8=64 etc: so 64=1.78x the light of your 36.
Also, I just remembered that your 6" is photographically slower at f/6 than my 8" is at f/5, making the difference even greater.
raymo
Last edited by raymo; 27-03-2019 at 04:10 PM.
Reason: more text
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