Quote:
Originally Posted by sheeny
What you're looking for I'd hardly call ultra wide especially when it comes to binoculars.
For light grasp you need the biggest objective you can afford. A full dark adapted eye is 7mm diameter pupil (when young!), so 49mm2.
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You also want the largest usable exit pupil you can get. there's no point having an exit pupil bigger than the pupil of your dark adjusted eye, so choose binos with an exit pupil as close to 7mm as possible - better under than over..
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Thanks for your reply
Hey, I'm happy to take the biggest light grasp (objectives) I can get! - it just seemed from my reading that they dont actually make them that big - maybe I'm wrong! I currently have some Saxon 20x80's, but i find their TFOV too narrow. I had a Pentax XW40 that delivered a, 8mm exit pupil with my dob and the results were not good and so i have avoided larger than 7mm exit pupils ever since. I figured that once the exit pupil touched the edges of my pupil something happens (maybe on account of getting my eyes lasered years ago?) and I've avoided it ever since - hence looking more at 5mm. But does that limit my choices?
The light grasp is important because it would be good to be able to perhaps see a faint smudge of a target where it is supposed to be before i train the scope on it. But yes, that is secondary to having a wide field.