Quote:
Originally Posted by rogerg
Well surely the point of a larger scope is you have higher resolution at a reasonable focal ratio - you have that longer focal length but at something useable rather than F/32 or such.
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Resolving power is directly linked to aperture and optics' quality but I think it is independent from light gathering capabilities.
Quote:
Originally Posted by rogerg
If a 12" at F/10 were to record brighter stars than a 8" at F/10 then why does a 60mm (aperture) lens @ F/2.8 record brighter stars than a 60m (aperture) lens @ F/4?
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I don't think you can compare it like this. On one side you're modifying FL as well as aperture and on the other side you're modifying only FL. 12" will always gather more light than 8". A 60mm lens at F/2.8 is faster than the same lens at F/4 because in the latter you've decreased the image scale on your sensor.
To recap you want more light in get more aperture. You want more fine details. Match your camera pixel size and scope FL to get a better image scale. Regardless of aperture.