Whether you have a new pair of binoculars or one you have used for a while in your outdoor adventures, you might discover that the vision is misaligned. In short, the binoculars have lost collimation and are now providing you with double vision. To fix the problem, you will have to re-collimate the binoculars.
Collimation is a process used even by the astronomers to fix the scopes of their telescopes. When a telescope is well collimated, the light will pass through the objective lens, into the viewing lens, and straight to your eyes. When a telescope is poorly collimated, a mirror or lens might not be sitting in the correct position. As such, the light isn’t traveling from the objective lens to the mirrors in the right manner. Simply, the mirror isn’t sitting correctly in the barrel.
When it comes to the binoculars, you are now dealing with two columns that work together to create an image. However, the problem might not be an incorrectly positioned lens or mirrors. Rather, the problem is that the binoculars aren’t properly collimated. To show you how to fix double vision on your binoculars, we are going to take you through the steps for re-collimating. You have two options – you can either align prisms by adjusting screws or disassemble the optics.
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Fixing Double Vision on Binoculars
Step 1. Gathering Tools
There are several tools that you will need to re-collimate your binoculars. They include the following:
- A small flathead screwdriver to help you break a locking adhesive or glue and adjust tilt screws.
- Your pair of binoculars with roof or Porro prism.
- A tripod stand and a tripod adapter.
- An L-bracket clamp or hinge to firmly hold the binoculars.
- A head-torch for lighting the working area hands-free.
- A penknife or hobby knife to remove glue or adhesives from the tilt screws.
- A ruler
- A tape
- A laser-beam generator
Step 2. Gather the Required Materials
Before you start adjusting your binoculars, there are several materials you are going to need. They include the following:
- Use a transparent film to print out some Bahtinov masks. Make sure that the masks have even spaces between the three tabs. That way, they will be easy to tie to the binoculars.
- Elastic bands or tapes with stickers for attaching the Bahtinov mask onto the binoculars.
- You can replace the Bahtinov masks with different colored filters. For example, you may choose 3D anaglyph glasses or cellophane.
Step 3. Check That Collimation Is Lost
Signs of lost collimation can be as obvious as a bend in the tubes. Where there is external damage, test the binoculars in the night or day sky. Check that the pupillary distance between your eyes matches the binoculars. However, your brain might end up merging divergent images. You can trick it to know that the images aren’t identical by doing the following:
- At night, pick out the brightest star and try refocusing either to the left or right ocular lens. Where there is an optical misalignment, the image of the star will move away from the center when you focus on one side.
- Pick one star and color-contrast its image by using differently-colored filters on the two lenses. You can use differently-colored cellophane of or 3D anaglyph glasses. This option is great when testing your binoculars during the day.
- Arrange Bahtinov masks to stand at an angle of 90° against each other. You will have to start by printing out the masks.
Step 4. Locate the Tilt Screws
Most binoculars come with the prism tilt screws hidden under a layer of rubber, glue, latex or adhesive. This is meant to provide protection against weather elements and to prevent intentional or accidental adjustment. The prism tilt screws usually come in two or three pairs. They are meant for horizontal or vertical adjustment. Those found closer to the eyepieces are meant for horizontal adjustment. Vertical adjustment screws are closer to the objective lens.
In this case, you are supposed to adjust the horizontal adjustment screws since they are likely to be misaligned. When slicing the opening, check that you don’t cut yourself, accidentally catch the screws or spoil the covering. So, focus only on the precise location of the screws. Repeat the action on the other horizontal adjustment prism tilt screw. The flathead screwdriver should be of the right size.
Step 5. Mount Binoculars on Tripod and Pick a Target
The next step is to mount the binoculars onto a tripod and pick a target. You can use a bubble leveler to ensure the binoculars are standing vertical and level with the tripod. If you have no bubble leveler, use a makeshift plumb bob to ensure the neck of the tripod is vertical.
Choose a stationary target that is either aquatic or terrestrial. It should be at least 1000 yards or 3000 feet away for a pair of binoculars with at least 8X magnification power. If the magnification is lower than that, the distance shouldn’t be more than 167 yards and 500 feet. You may target a rig cross or Polaris.
You can use a laser beam to focus on the target. A well-lined up target will be visible in either eyepiece. One side will be left of the target. The other will be on the other side. Pick the side closer to the target and align it to the center. Adjust the other side horizontally if outside the target to the left or right. If above or below, you should adjust it vertically.
Step 6. Adjusting the Binoculars
As you turn the screw (at most 1/8-turn) look through the binoculars with both eyes to see the effect your action has on the image. Take note of what happens with each turn and revolve the screw back to its original position. Then, turn both screws simultaneously until both images are merged fully.
Step 7. Test the Binoculars
Check the binocular vision looking through the two eyepieces and moving your eyes back in slow motion. You should be able to see columns of light coming straight at your eyes in both columns. If any of the columns has a bent light column, the problem could be beyond what you can change.
When you know the procedure of adjusting binoculars with double vision, you will be able to avoid buying a brand new one. That way the images of the two sides of the binoculars will merge and enable you to keep enjoying your favorite hobby – whether it hunting, camping with your kids, or bird watching.