How To Fix Binoculars With Double Vision

How To Fix Binoculars With Double Vision

If your binoculars have double vision, you have a problem, they’re too big to make a good ornament but all is not lost. Firstly are they still on warranty? If they are, contact the manufacturer. If they are not still covered by warranty, read on for the easiest step by step guide to re-collimate your binoculars.

What Is Collimation?

In binoculars collimation is the alignment of the 2 images from each tube merging into one. If there is a misalignment, it will be more apparent under the night sky than during daylight hours. If the images are out of alignment, and it’s only slight, your brain will try to compensate for it, this will strain the muscles that are responsible for moving the eyes which can lead to headaches at best and nausea if not remedied soon enough.

If your binoculars are misaligned from day one, they should be returned to the vendor immediately and be repaired (under warranty). The reason we keep referring to the warranty is that the following procedure will invalidate any warranty. It will work 100% but you may wish to take it to a professional for repair. In most cases, this will cost you more than the purchase price of the binoculars, but the choice is yours.

What Does Collimation Mean?

It all derives from astronomers, they talk about collimating their telescopes. They say that a well collimated telescope allows a column of light to travel through the objective lens and reflect off any mirrors or pass through any prisms then enter the viewing lens straight into your eye. A badly collimated telescope will show a dim image, making the viewing scope appear hazy. 

In theory this problem will be twice as bad with binoculars, as they have 2 tubes so double trouble. But fortunately that is not usually the case, with binoculars the problem is usually one of the prisms is out of alignment.

Fixing Prisms That Are Out Of Alignment

Most binoculars use the Porro-Prism system to create an image that is the right way up and not back to front. This system works incredibly well but is usually the cause of binoculars seeing double. In lower priced binoculars,a slight knock, either from being dropped or involved in a collision with a wall, rock face or something similar.

In these lower priced binoculars,each prism is held in position by a spring clip that is tensioned against a screw that is used to tilt the prism. This allows them to be easily dislodged by slight (or not so slight) impacts. Which is not so good for the binoculars, but is good for us to repair without too much difficulty.

Before attempting a repair, check the binoculars over for any obvious signs of damage, like one of the objective tubes has been bent out of shape. If that is the case, then we are not going to be able to repair it here. Under those circumstances we advise you to either take it to an expert, or replace them with a new pair.

 How To Repair Binoculars With Double Vision

  1. Check The Warranty
    Make certain the warranty is out of date before commencing any of the following steps, as by performing the following steps you will invalidate any warranty.
  2. Check The Users Manual For The Location Of The Screws
    The adjustment screws are usually covered with either glue or some sort of plastic covering. This is to prevent accidental movement of the prism. If the users manual does happen to show the location of the adjustment screws, it will make the job much easier. If you don’t have the manual or it doesn’t mention the adjustment screws, check online for a diagram of your particular binoculars.
  3. Remove The Plastic Casing Or Glue
    To reveal the screw heads that are on the back rim of the binoculars. This is where the horizontal adjustment screws are usually located.
  4. Remove The Glue Or Plastic Casing
    To reveal the screws that are nearly even with the focus knob in the centre of the binoculars.
  5. Mount The Binoculars On A Tripod
    If you don’t have a tripod just affix the binoculars to a piece of wood that is fixed firmly in the ground.
  6. Pick A Bright Star
    You’ll need a clear night for this and then aim at the brightest star you can see focus in as well as you can. This can be done during the day just aim at a solid object that is stationary around 1 mile away.
  7. Knock the right-hand lens out of focus
    Close your left eye, and turn the right lens to the right so that the star becomes completely unfocused. Then open the left eye, you should now see one focused and one unfocused star.
  8. Check The 2 Images
    If your binoculars are suffering from being uncollimated the 2 images will not be lined up. If the collimation was correct the focused star should be sitting dead centre of the unfocused star. If not, it’s time to make some adjustments to the 4 screws you uncovered earlier.
  9. Turn Each Screw Slightly, One At A Time
    To see if it makes any difference to the image. Turn each screw a ½ turn, check the image, if it’s not made any difference, turn the screw back a ½ turn and move onto the next screw. There is a lot of trial and error in this refocusing malarkey. Be patient.
  10. Tighten One Of The Horizontal Screws Until The Images Are Closer
    Start with the horizontal screws as these are usually the ones that get affected. Only aim to get the image ½ way closer, because the screws should be adjusted equally to get a clear image.
  11. Adjust The Other Horizontal Screw To Align The Image
    Turn the opposite horizontal screw until the image is gradually getting closer. Stop once the images are even. 
  12. Turn The Vertical Screws Until The Images Are Centred
    Adjust each screw slightly until the images are perfectly centred.
  13. Refocus The Right Lens And See If The Image Is Clear
    Once the image is centred, refocus the right lens and check that the star is clear again. To check collimation has been completed look away from the binoculars for a minute, then look back at the star. If it is one image, collimation has been successful, if there are 2 images that become one after a short time, then you might have to adjust some more.

Frequently Asked Questions

Why do I see double when looking through binoculars?

If you are seeing double through your binoculars they are usually out of collimation. This can be repaired at home, but it’s a tricky job. If you don’t feel confident you can take them to a specialist and get them repaired.

Can you repair binoculars?

Binoculars can be repaired in most cases.

How do you fix blurry binoculars?

To fix blurry binoculars you need to adjust the middle focusing ring whilst just looking through your left eye. Once that is focused using just the right eye, adjust using the diopter, now the image should be clear.