Any good quality binoculars with large second number (nx50 or better) would probably do. Various manufacturers have different light transmission factors. But a general rule is that for night vision, the relative brightness index should be high (RBI = (exit pupil)^2 (i.e. squared), where exit pupil= diameter/power). For a 7x50 binoculars, it is (50/7)^2 ~=51 (which is fairly high); for 7x42 binoculars, this is 36; for 10x50 – only 25.
Unfortunately, very few manufactures would provide the light transmission factors, so there is no easy way to compare (on paper) which unit is better than the other. If you Google this, you would probably find (as I did) that most recommendations are for 7x magnification for marine use. This makes sense for two reason: one – we have a problem providing a stable platform required for a clear view at high magnification (think how difficult it is to keep a long lens (400 mm or higher) in your camera aimed at the faraway object) and two – the higher the power, the lower the RBI. just a thought. Marek ------------------------------ Message: 2 Date: Fri, 14 Mar 2014 07:41:53 -0400 From: "Della Barba, Joe" <[email protected]> To: "[email protected]" <[email protected]> Subject: Re: Stus-List Handheld spotlights + binocs Message-ID: <1073606396712942aee54d9a960e45a71e1c292...@hq-mb-07.ba.ad.ssa.gov> Content-Type: text/plain; charset="us-ascii" I'll have to look. They were a birthday present and were whatever the top line West Marine binoculars were at the time. Any high quality 7x50 set with good coated lenses will make something you can just maybe barely see stand out plain as day. Obviously rain, fog, pitch dark, and looking into moonlight will defeat them. Some people think "moonlight = good", but only if it is from behind you! What I need to do is train my dogs to point and bark at unlit markers. I asked our vet why they can run full speed in the woods in the dark and he said dogs and cats see about as well as a human with night vision goggles on. Speaking off night vision, I rarely use any kind of spotlight. I do much better with making sure my night vision stays sharp. I have red LED lights for everything - there is NO white light allowed after dark. Something I learned when I was flying out of an unlit grass field is to look "off center" and kind of scan besides what you are looking for. Human vision is much more light sensitive off-center than straight ahead. PS - Another night vision killer is the various plotter-computer video displays. Make sure you can turn it down! I have seen powerboats go by at night with the helmsman's face lit up bright as day by all the screens that he was looking at. I doubt he could see the bow! Joe Della Barba Coquina C&C 35 MK I
_______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected]
