In order to make binoculars compact, prisms are used to refract the light sideways and shorten the length of the tubes. This cuts down the light level a lot, and interferes with their use at night. Reflecting telescopes send the light back the way it came, and so are already shorter than they would be if they used lenses. This principle could be applied to binoculars, thus eliminating the need for big chunks of glass stopping a lot of the light, allowing them to be used in poorer conditions with a brighter image.
-- nineteenthly, Nov 06 2005

Binocular reflecting telescope http://www.astronom...nocs01/DSC00009.JPG
I don't think that's what you had in mind... [wagster, Nov 06 2005]

Like this? http://www.opticspl...ukon-30x50-nrb.html
Not exactly "widely known to exist" though. [wagster, Nov 06 2005]

Does this mean you will be looking back at your own eyeballs?
-- Elitefingerbun, Nov 06 2005


Lessee... how about a pair of miniature (40 mm aperture?) Maksutov-Cassegrains held out there in front of your face - it's going to make a quite a double handful. Even better - a pair of matched 4.5 inch folded Newtonians with right angle erectors, one over each shoulder with your head stuck up through the middle of the frame. Imagine that looking at you out of the gloom.
-- lurch, Nov 06 2005


I've only used a couple of reflectors - a camera lens and an astronomical telescope, both waaaay to big for binoculars. I don't see why they couldn't be miniaturised though, but neither do I see why they aren't available already. I'll have a google and if I come up blank you get a bun.
-- wagster, Nov 06 2005


There's probably some highly technical reason why this can't be done. I know that mirrors used like this suffer from different aberrations to lenses. AS far as I can tell, though, it's a brilliant idea. Major bun. See if there're any patents available.
-- moomintroll, Nov 06 2005


Thanks for the links, [wagster]. I notice, though, that the portable version seems to have been discontinued, which is a shame, but i'd like to know why. I wonder if there was a technical problem. It also means that it doesn't exist any more.
There might be a problem because they would be portable and could be easily jarred out of alignment, and there would be a different kind of aberration than refracting binoculars. I'm not clear what sort of aberration mirrors have though.
-- nineteenthly, Nov 06 2005


You'd think mirrors would lend themselves to portable binoculars, seeing as they're so much lighter than lenses or prisms.
-- wagster, Nov 06 2005


In terms of weight yes, but i'm thinking of the problem keeping a suspended secondary mirror at the right angle. Come to think of it, i have no idea why conventional binoculars don't use mirrors rather than prisms.
-- nineteenthly, Nov 06 2005



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