Wikipedia:Reference desk/Archives/Science/2021 August 5

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August 5

angled eyepiece binoculars

There are some very expensive binoculars[1] with angled eyepieces, nice for stargazing without having to tilt your neck so uncomfortably. That one is extreme as I've seen some other ones in the $1000 range. But is there some reason I don't see them at more normal consumer prices, say $100 or so? I have a pair of decent yet affordable 7x50 binoculars with straight eyepieces and am wondering whether angled has to add a lot to the cost. Thanks. 2601:648:8202:350:0:0:0:2B99 (talk) 22:53, 5 August 2021 (UTC)

It's pretty common in spotting scopes, but I've not seen anything smaller than observation or astronomical binoculars that require tripods with angled eyepieces. --jpgordon^{𝄢𝄆𝄐𝄇} 04:26, 6 August 2021 (UTC)

Right, but even astronomical binoculars don't have them, except for quite expensive ones. So I am wondering whether the feature was inherently expensive. 2602:24A:DE47:BA60:8FCB:EA4E:7FBD:4814 (talk) 20:13, 6 August 2021 (UTC)

If you can put one on a $100 spotting scope, not inherently expensive. --jpgordon^{𝄢𝄆𝄐𝄇} 21:32, 6 August 2021 (UTC)

Oh, one discussion I read said it's a focal length issue. --jpgordon^{𝄢𝄆𝄐𝄇} 21:38, 6 August 2021 (UTC)

Fair enough, thing is I can't find anything like this (price-wise) with angled eyepieces. Those are 20x80mm so long focal length, big, etc. Same shop has a 70mm pair with angled eyepices but that is $1000+. Oh well, I'm too far from any good dark skies these days to worry about this. Maybe I'll get a folding lawn chair if I start using my 7x50mm more, to make it easier to look straight up. 2602:24A:DE47:BA60:8FCB:EA4E:7FBD:4814 (talk) 23:58, 6 August 2021 (UTC)

One expedient is to mount a large flat mirror at an (adjustable) angle in front of you thus: <∘)----^↑/, and point the binoculars at that. Ideally it should be front-silvered, but you might find you can tolerate the fainter doubled reflection from a conventional back-silvered mirror.

It might also be possible to firmly mount such a mirror actually on the binoculars, just in front of the objective lenses, but I've never seen that actually done. {The poster formerly known as 87.81.230.195} 2.122.62.68 (talk) 22:12, 7 August 2021 (UTC)

The principal issue with such a strategy is that you will end up sacrificing field of view and (possibly) brightness. Inserting a mirror between the eyepiece and the viewer will almost certainly move the user's eye back past the maximum eye relief distance of the binocs; they will be left 'peeping through a keyhole' from a distance.

A minor additional irritation with such an approach is that inserting a single mirror will invert the image. Users of various flavors of astronomical telescopes will be used to having their images inverted in various ways and may not be bothered, but people who are used to the upright images of binoculars or spotting scopes may be discomfited by the change. TenOfAllTrades(talk) 12:29, 8 August 2021 (UTC)

The mirror is placed in front of the binoculars (see Objective lens), not between the oculars (eye lenses) and the eye: sorry my artwork wasn't up to making this clear. As you say, this inverts the image, but anyone using or intending to use most astronomical instruments will have to get used to this anyway. {The poster formerly known as 87.81.230.195} 2.122.62.68 (talk) 02:45, 9 August 2021 (UTC)