How to test for collimation

[etc]

This is really simple, I checked mine with success.


It is sometimes a bit difficult to determine if binoculars are well-collimated or not. Partly this is due to the fact that the brain can very quickly adapt to mis-collimated optics, albeit with eye strain that in time becomes disconcerting. When adjusting the collimation, one often has to resort to tricks to avoid having the brain "fix" the problem too quickly.

However, there is a very simple way to overcome this: select a fairly bright star, focus one barrel to be as sharp as possible then throw the other barrel significantly out of focus. When you do this, the natural tendency of the brain to align the images is blocked and you will then see the pinpoint image of the star superimposed over the out-of-focus image. Even a slight mis-collimation is then easily detectable as perfectly collimated optics should show the sharp star image perfectly centered in the fuzzy blob of the other image. You can reverse which barrel is out of focus to be sure that there is no lateral image shift when changing the focus.



From
http://www.cloudynights.com

[kabsetz]

This is a promising method, but be careful to keep your eyes well centered on the exit pupils when using it. Otherwise, you may get incorrect results. I haven't used this method for long enough yet to have reached a conclusion of its reliability, but will keep checking it against other methods. If it turns out to be good enough, it certainly has the advantage of being very quick and easy to perform. Another caution to keep in mind is that a perfectly collimated binocular is a rather unlikely beast, and once you have done enough repetitions with the test to have a consistent result, you need to interpret the less-than-optimal result and figure out if it is good enough. If Henry Link has tried this method, perhaps he could also comment on it?

Kimmo