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How to Collimate Binoculars

Binocular collimation is a pretty scary experience because it requires special equipment and skills to do it. If you are a fan of outdoor activities, it's a good idea to know how to care for your equipment, and learn how to collimate binoculars.

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What Is Collimation?

Collimation is a term that defines the alignment of an optical element along the optical axis. To tell if your binoculars or optical device has a collimation problem is that every time you look at an object through the lens, you'll see a double image or misalignment. To solve this problem is usually done by adjusting the objective lens according to your view.

What Causes Binoculars to Lose Collimation?

There are several factors causing your binoculars to lose collimation. For example, if your binoculars fell while you were running, it is possible that the prism has shifted. If this continues for a long time, the prism will move with each drop, and eventually, your lens will become completely misaligned.

Another factor that causes misalignment of the lens is often the case when you are trying to clean binoculars. For example, if you feel you need to clean the inside of the lens due to fog formation, this could cause a misalignment.

Here is a simple step by step procedure on how to colimate binoculars.

How to Collimate Binoculars

Horizontal Collimation

  • Go outdoors in daylight and focus your binoculars on any large object with distinct horizontal and vertical edges, at a distance of about 100 yards.
  • Relax your eyes. Alternately open and close them, about every second. You should see the image move slightly to the left when opening the left eye and to the right when opening the right eye. This slight movement is normal and desirable.
  • Adjust the prism tilt screws to restore collimation if you detect horizontal movement.

Vertical Collimation

  • In the daytime and outdoors, look at a distinct horizontal line, such as a roof line, gutter or fence rail.
  • Slowly move the binoculars about 4 inches away from your eyes as you keep looking at the images in the eyepieces.
  • Check that the horizontal feature you focused on remains an unbroken straight line -- in other words, no part of it is displaced vertically.
  • Adjust the prism tilt screws if you detect any vertical displacement.

Prism Tilt Screw Adjustment

  • Locate the two prism tilt setscrews just ahead of the eyepiece on each barrel. For rubber-armored models, pry open the rubber covering with your screwdriver to expose them. Be careful not to overstretch the rubber; you want it to snap back to its original position when done.
  • Remove the protective glue from the setscrew's top and insert the screwdriver in the slot.
  • Turn the right barrel's setscrew clockwise in very small increments to move the image in the right eyepiece to the left and down, counterclockwise for up and right.
  • Turn the left barrel's setscrew in the same manner, clockwise or counterclockwise, to adjust the image's horizontal and vertical alignment in the left eyepiece.
  • Adjust one or both setscrews as necessary, frequently checking progress using the horizontal and vertical collimation tests, until the two images merge horizontally and there is no vertical displacement.


With the step-by-step guide above, you can learn how to colimate binocular. If you don't have the patience to go through the whole process, there's no guilt in finding someone to do it for you. You may also invest in other reliable brand binoculars.