Telescope Reviews: How to Focus Binoculars

It can be surprising how many people new to using binoculars, or even some who have had them for a long time, do not know the correct procedure to focus binoculars. At every session I teach, there are always a group of people that do not know how. Erik D recently posted this procedure and it was a big help. I'll repeat the post here, but first; A few other things users should know about focusing:

Of course, this relates to binoculars with a Center Focus wheel that moves both eyepieces and a Right Diopter adjustment that moves just the right eyepiece.

If you have binoculars with individual eyepiece focus, just use each separately as if each were a diopter adjustment. Actually, that's exactly what it is.

Best focusing can be achieved by focusing "IN". So start with the eyepiece turned out and "FOCUS IN". Stop when you hit a pinpoint image. Rocking back and forth over the best focus point is not recommended. We have decades of military testing to thank for that little tidbit.

And now from Erik D.

1. Cover the right objective.

2. Look thru the binos while keeping both eyes open and RELAXED.

3. Use the center focus wheel ONLY to achieve sharpest focus. Do NOT try to compensate for out of focus image with your eyes. Let the focus wheel do all the work. Best focus is achieved when star image is the smallest pin-point. This is the same process as if you are looking thru a single EP of a scope. It should be pretty easy to tell if you have achieved best focus because you'll see spikes and flaring of star image otherwise.

4. After you have achieved best focus with you left eye uncover the right objective and cover the LEFT objective.

5. Using the Right Diopter Adjustment (RDA) on the right EP ONLY, focus the image thru the right barrel. Remember to keep both eyes OPEN and RELAXED. Only the RDA should be doing the focusing, not your eyes. Do NOT touch the center focus wheel while your are doing the RDA.

6. When you have achieved pin point focus in your right eye you can remove the cap on the left objective and images in both eyes should be in focus.

The goal of this procedure is to use the RDA to compensate for any difference in eye strength between the left and right eye. You do not have to match them or make them "equal" (by setting them both on the same number).

Make sure your binos are on a solid mount/rest before you attempt this procedure. No one can hand hold 8.8 lb binos and perform critical RDA at the same time.

Erik D

Thanks Erik.

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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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