Annoying eye-brain coordination

[jonathan]

It feels like I've always had difficulties seeing one circle when looking through binoculars, that is until I purchased my Bushnell 8x42s; I can easily look through those at any target without having to concentrate on being at one with the single image (although on some odd days I do have to think about it for a few seconds).  I've had a pair of 15x70s lurking around the place that I'd never managed to see a single image in, I just put this down to the larger aperture.  I recently purchased some Pentax Papilio II 8.5 x 21 binoculars for nature use but found the old stereo vision thing cropping up again, I concentrated on seeing one circle and to my relief it resolved into a single image and circle (they are really nice binoculars by the way).  I thought I'd give my 15x70s another go the other night, I found to my amazement that I could resolve the stereo view into a single circle and image but annoyingly only for terrestrial targets, the instant I try to see any stars even with terrestrial objects still in view I get two of them, and the longer I look the further apart they appear to get.

Any opticians or psychologists in the house who can shed any light on this?  I really don't think there is anything wrong with the binoculars, just my strange eyes and brain not liking binoculars, but if there's a solution then I'd like to know it please.

[BinocularSky]

Although it may be your eyes/brain, it does sound like miscollimation: astro targets are typically much more demanding than terrestrial and, if they are budget binos, they are notoriously easy to knock out of collimation (if, indeed, they were ever properly collimated. If you want to try collimating the 15x70 for your eyes either look  here or  give me a shout; it's actually quite easy and, if the binos don't work for you now, nothing you can do to them will make them more useless - and you may just get them usable.

[jonathan]

The Pentax ones were certainly not cheap, although not mega money.  This seems to happen too often with too many very different pairs of binoculars, the common factor in all cases is me.  It may be true that a very expensive pair of binoculars may be super collimated and work perfectly for me, but if it's just down to the quality of the glass or mirrors etc then I have no chance.  I have attempted to check collimation of another pair of binoculars before but they appeared to be already well collimated.

[Merlin]

It's possible that you might have my problem. Some years ago, a muscle "relaxed" in the right eye. This meant that many of the binoculars I looked through were giving double star images. At first, I thought the problem lay with the bins, but an optician confirmed that it's my right eye that's out of collimation.

I'm not saying that you have this problem, but you might have. I suspect that my problem was caused by pressing bins with rubber eye-cups too hard against my eyes, causing a suction effect. We live and learn.. .

[jonathan]

Actually, I just did a search on 15x70 binocular collimation to see if there was a simple test I could try out, came across a short youtube video describing to look for vertical misalignment (which there wasn't), then another thread on this forum which pointed to a web page describing how to easily adjust for vertical or horizontal alignment - http://www.oberwerk.com/support/collimate.htm

What do you know...  I worked on the assumption of horizontal misalignment so turned both screws inwards, the more I turned them, each time I looked in the binoculars the easier it was to make just one image to the point where I didn't have to think about it at all, it was just there every time.  The big test will be tonight (if there are any stars out), I'm confident it is now 200% better than 10 minutes ago.  The screws are just under the rubber armour on each shoulder of the binoculars, the rubber isn't glued down there as they obviously expect people to need access to these two screws.  As for my previous attempts to collimate binoculars, maybe I didn't do it properly as I don't recall turning those two little screws inwards.

I'm now wondering if I could adjust my other binoculars in the same way, maybe they all lose a bit of collimation just in transit from the factory, or maybe they're never set properly in the first place, maybe my eyes are more sensitive to this kind of thing, who knows!

Thank you BinocularSky for the collimation hint, although I think in my anger at myself / big binoculars I didn't actually check that link originally; hope this thread helps someone else too (you can never have too many helpful threads!)

PS... something that bugs me is that I've asked others to look through these binoculars and they reported no problems...  do they have better brains or have they just never properly seen a single image (maybe they block out one eye?)  Odd!

[jonathan]

I'd like to report complete success, the 15x70 (Revelation Astro) binoculars now work perfectly for night time viewing, didn't see even a hint of double vision and that was awkwardly looking out of my skylight which is tricky at the best of times (I had the light off though).  Now I just need to get a better tripod to use them on and I'll be set for even more grabbing and going than before!

Thank you again.