How to align binoculars so both sides point in the same direction

by Steve Coffman, last updated on

Aligning binoculars at home is all about checking whether there’s a serious misalignment and making the most out of your warranty. If you examine your binocular externally, you may not notice that it’s misaligned. Unless the tubes are badly damaged, it’s difficult to tell. But when you look through both eyepieces, and you feel as if the optics are pulling your eyes out of their sockets, then you know there’s a problem. Or maybe you experience double vision on your binoculars.

Our brains tend to compensate for the separation of identical images from both eyes. The greater the separation, the more apparent the eye strain, nausea or headache. Strain results, because human eye muscles and brain try to merge the separate images into one. Nothing is more annoying than a poorly aligned binocular. When both telescopes making up the binocular aren’t precisely parallel, your eyes and brain would struggle to mate the two images of the same object. Double vision, dizziness, eye strain, nausea or headaches often result.

What Causes Loss of Alignment?

There are two main causes:

  • Dropping, hitting or sitting on your binocular. Cheaper binoculars usually have spring clips, which hold tensions in the prism tilt screws. Impacts of knocking or hitting can remove the prisms from their positions.
  • Exposing the light-sensitive intensifier tubes, photocathodes or any other internal component to bright light. When light beams fall on the objective lenses, they are focused. And so, when light hits the photocathode tubes, the photons release energy, which are enough to power electrons through the intensifier toward the phosphor screen. When there’s too much light, there’s too much photon energy, which can heat up the material makeup of the components. When components expand or melt, misalignment results.

You’d need specialist equipment and skills to check whether both sides of your binocular are pointing in different directions slightly.

You can’t fix alignment problems at home.

But what you can do is detect extensive misalignment and take advantage of your warranty.

Let’s see how you can check whether your binocular’s optics aren’t parallel.

Select a Distant Target and Look through Both Eyepieces

Our eyes tend to readjust angles, so you may not notice a slight deviation. You must trick your brain to maintain your viewing direction along both parallel lines.

misaligned binocular
Misaligned binoculars
  • Ensure the distance between the pupils of your eyes match with the eyepieces. During daytime, our pupils contract to a diameter of just 0.08-inches (0.2cm) to regulate excess light. And so, a beam of light falls in large part on the iris, leaving only the center part to enter the pupil. Therefore, you won’t notice a difference in brightness of images between a 2.5×40 binocular whose exit pupil diameter is 16mm and a 2×24 binocular with 12mm.
  • Select a target that’s 3000-feet (1000-yards) or more away
  • Mount your binocular onto a tripod
  • View the target through your binocular. You can perform the test during under a day sky. You can select the edge of a roof of a house or a power line as a target.
  • Move your eyes away from the binocular as you view your target in the middle of the exit pupil
  • Continue moving your eye away and stop at a distance of 8-inches (20cm) away from the eyepieces. At this point, tilt your head or binocular slightly. You’ll notice that the circle around the image begins splits into two equal parts. The horizontal line across the image, as in the roof edge or power line, doesn’t break. If that’s the case, your binocular is in alignment. However, if the horizontal line breaks such that one piece is above or below the other, then your binocular is out of alignment. And since there’s conflict between both images, your eye muscle and brain would strain to reconcile the broken parts into a one line. Depending on the extent of separation, the severity of your headache can vary. In worst case, you’ll experience dizziness or nausea. And next time when you want to observe objects using your binocular, you won’t feel like, because of the uncomfortable experience. In the end, you would view your binocular as unfit for use. And that’s a bad thing.
  • Even when you lean your head or binocular, you shouldn’t see a broken horizontal line if it’s properly aligned. While the circles would become uneven, that shouldn’t be a cause for an alarm. But if your binocular is out of alignment, you’d see a discontinuous line.
  • There must be 100% overlap between both images of the same target and between the two exit pupils. As long as overlap isn’t full, your binocular is out of alignment.

What can I do About Misalignment?


Nothing you can do at this moment. You’d require professional help. But before you seek professional repair, make the most out of your warranty.

Some manufacturers can fix for you the misalignment problem for free or at a small fee. And that’s a good thing, given that the costs of professional repairs can surpass the price of your binocular.

In such a scenario, it’s not worth your money to repair while you can replace your binocular with a brand new one.

Unless you’ve a special attachment to your binocular, you can buy a binocular that’s in collimation rather than have an old one realigned.

Cheaper binoculars are more vulnerable to fall out of alignment. They use tension in the tilt screws hold on in position a spring clip, which can get out of alignment when you drop or knock your binocular.

Expensive binoculars are less susceptible to loss of collimation, because the manufacturer has machined them with tough, resistant and quality materials.

So, when you drop them, your instrument won’t lose collimation, because the materials are able to withstand shock. Even in cases where they fall out of alignment, the manufacture has willingness to repair.


When you talk of how to align binoculars, both sides must point precisely in the same direction. If the optics of both sides aren’t perfectly parallel, then the binocular is out of alignment. This is specially important when using them to help you calculate MOA.

Unless your binocular is damaged physically so can notice externally, it’s not easy to tell whether there’s misalignment. And more so if misalignment is slight. You’d require a very precise equipment to detect such unnoticeable loss of collimation.

Only when misalignment of optics is extensible is when you can notice. In such a case, you won’t require professional help. Nevertheless, you can do nothing about fixing misalignment other than to leave it to a professional hand.

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