Binocular alignment Q.

[Romanus]

I've read in several sources that the way to test to see if your binoculars' light paths are aligned is to open and close your eyes (or, alternately cover one lens and the other), and see if you see a double image that your brain merges into one.

I've tried this on several times, and still haven't been able to determine if my binoculars (Orion Scenix 7x50, btw) are aligned or not. Looking at landscapes, I notice no double images. Looking at stars, I do notice two images that quickly merge into one, yet don't notice any eye strain aside from the usual stress of holding them steady or looking near the zenith--yet, I do briefly see two images. In fact, even opening and closing my *eyes* yields two images that merge into one.

So, my question is this: given inevitable subjectivity, how do you determine what constitutes misalignment and what's just regular stereo vision? Experience with truly misaligned binoculars would be much appreciated.

Thanks in advance!

[Mr Q]

Romanus - You have the right idea. The fact that you can quickly, mentally merge the stars together means the alignment is probably not off enough to worry about. A little more out of alignment and you would quickly get a headache even though the stars merged by your brain.

So from what you posted, I'd say you are well within the boundaries of having your binos within practical collimation limits. Besides, adjusting them can be difficult and risky (damage) unless you have had some experience doing it before. Also, your binos may not even have prism or objective adjustments to begin with.

Hope this info helps you out. For more info on the subject, visit "Cloudy Nights" forum and scroll under "Binoculars". There are several threads at the top of the first page with a wealth of bino optics info.

Mr Q

[tdvance]

There are two ways I can interpret "misaligned".

One is that the two tubes are too close together or too far apart. Of course, this is easy to fix on all but the very cheapest binoculars, since the inter-ocular distance can be adjusted. A technique is to look in the binoculars, pull them apart so you see a "master card" shape, and push them back together till the two circles merge into one.

The other one is more serious--the two tubes point at different angles. That would be hard to detect if it's slight--I'd say if it's not giving you a headache or causing other problems, no worry--it's rare for binoculars (that haven't been dropped) to get that far out of alignment, and the double-image that disappears can easily be caused by your eyes changing form focusing at something a foot away (like the pair of binoculars) to something an (effectively) infinite distance away even in perfectly-aligned binoculars.

If they need to be aligned--I'd recommend an expert--maybe at a high-end camera or astronomy store (generally not the one in the Mall, but one the pros, and serious ams, actually go to). Or even contact the company that made them.

[Mr Q]

A tip I use to check collimation is to stare at the stars (infinity) and bring the binos up to my eyes while trying not to refocus for distance. It takes a bit of practice but once learned, quickly detects any mis-alignment as even slight double images. Once learned, you can keep your infinity focus with or without binos in front of your eyes. Mr Q

[Romanus]

Thanks much, people! :)