Pro-tips on astronomical binoculars for those not in the know.
For deep sky stuff, you want the eyepiece exit pupil to be as close to but not larger than the dark-adapted eye pupil.
Too large, and you're wasting photons bouncing off non-light sensitive portions of your eye - like the exterior of your eyeball. To small, you aren't maximizing the light gathering ability of your dark-adapted pupil.
A ~7mm exit pupil is about the sweet spot. You can figure the size of the exit pupil by dividing the objective lens diameter in mm by the magnification. So a pair of 7x50 small binos falls really near that sweet spot, same with 10x70 but you'll need a tripod for anything bigger IMO. I personally wouldn't go below a 5mm exit pupil.
For deep sky stuff, you want the eyepiece exit pupil to be as close to but not larger than the dark-adapted eye pupil.
Too large, and you're wasting photons bouncing off non-light sensitive portions of your eye - like the exterior of your eyeball. To small, you aren't maximizing the light gathering ability of your dark-adapted pupil.
A ~7mm exit pupil is about the sweet spot. You can figure the size of the exit pupil by dividing the objective lens diameter in mm by the magnification. So a pair of 7x50 small binos falls really near that sweet spot, same with 10x70 but you'll need a tripod for anything bigger IMO. I personally wouldn't go below a 5mm exit pupil.
