Collimation (1 Viewer)

For reasons that escape me, I´ve been playing with my binoculars to test collimation. The way I understand it (which is probably the "not at all" way), you cover the objectives alternately and see if the image "shifts" a lot. So anyway, it did. With every bino I tested. Anyway, the moon came up this evening. And on a whim, I covered each eye alternately (without binos), and guess what, the moon leaped from side-to-side. It also appeared to be slightly "double". Then I put on my glasses, and the moon wasn´t double anymore. And when I did the "alternate-covering-of-eyes" test, it didn´t leap as wildly from side-to-side, only a little. So I did the same test of my binos as earlier, but this time with my glasses on, and found they all appeared far better collimated than before without spectacles.

Does this mean:
a) Bad collimation may be a feature of one´s eyes, not one´s binoculars
b) Some of us need to wear glasses all the time while birding, even if our
prescriptions aren´t particularly strong
c) I´ve too much time on my hands

Try it yourself if you wear glasses. It really passes the time.

Stars work well. When your bins are out of collimation there are double stars all over the place.

Sancho said:

Then I put on my glasses, and the moon wasn´t double anymore. And when I did the "alternate-covering-of-eyes" test, it didn´t leap as wildly from side-to-side, only a little. So I did the same test of my binos as earlier, but this time with my glasses on, and found they all appeared far better collimated than heretofore without spectacles.

Click to expand...

Check to see if either of your eyeglass lenses has a prism in it to correct a lazy eye. One of mine does. A prism will help correct the wild jumping you see without glasses. The way to check collimation is to put the binoculars on a tripod, make sure the binoculars are perfectly level, and look at a distant object -- I mean really distant -- so that there is no parallax. Then examine the scene through both left and right using the same eye (but not at the same time). :-O If you see any difference in view between the two (whether left to right or up and down), then you have a collimation error.

You are really playing dominant eye vs non dominant eye.

FOcus on a star, or a power line and move your eyes away from the eye piece keeping the object centered in the EP. If the star or the power line splits in two, you may have a problem. Likely not a problem with your EL

Sancho,
You just need binoculars to live, is all you have discovered. Have fun, but please don't go worrying about your binoculars. If you can
1)get the view quickly
2)watch continuously for 15 minutes or so with no funny feelings in your eyes
3)use the binocular all day long off and on as in typical birding, with no funny feelings
4)take the bino down and have your eyes normalize immediately, with no feeling of "straightening back out"
that's as perfect as it needs to get.
Ron

One thing I've been doing, which I've been thinking is a simple way to check the optically alignment, though I'm not so sure, is to look at a bright star normally through the bins (not the Sun, too bright), make sure both eyes can see the full views from their respective barrels, then tilt the bins up and down, left and right, tilt to each direction until the star just disappear from the view(s). If the star always disappear from both views at the same time, I take that the optics are properly aligned. Well, do you think my holds any water?

This has been mentioned elsewhere but a quick check is to defocus the dioptre on a star with left tube focussed and (using both eyes) see if the defocussed image has the star in the middle of it. If it does everything is OK.

Nev

SP,
I am not speaking from personal experience here, but discussions over on CN's bino forum clearly indicate that optical axis alignment between the two barrels, which gives the crucial eyestrain-free condition, can be disjointed from the alignment of the field edges. People who buy bargain Porros and adjust the prisms to align them often run into that confusing situation.
Ron