| EdZ |
| (Professor EdZ) |
| 07/09/09 05:05 PM |
|
Re: 6x30 or 9x50 finder scope?
|
Quote:
The light-gathering area is almost 3x as much in the 50mm --wouldn't that make the visual magnitude difference be over a full mag? Or is that not how that works?
Don't work that way at low powers, only at optimum magnification that could utilize all that aperture, and that would be, OH somewhere's around an exit pupil of 1mm.
Finder scopes are sort of like binoculars, except you only get one eye, so they allow you to see a bit less than binoculars. A 10x50 binocular under a mag6 sky can only see to about mag 10.5. Well an 8x40, under same conditions, can see almost to mag 10. Same with a 7x50.
edz