Binoculars occasionally require adjustment, or "collimation," to ensure the lenses are aligned.
Binoculars are really two small telescopes linked together and viewed by each eye separately. The optics of each binocular element must be properly aligned and the two units matched in order to produce identical images in both lenses. When the images are identical they appear to merge and the brain sees them as a single sharp image. Misaligned, non-merged images may appear jumbled and lack clarity or focus. Or the effect may be subtle, manifesting itself in increased eye strain and fatigue when using the binoculars for extended periods. The process of matching images on both sides and aligning the optics is called collimation. After many jolts and jostles in the field, any pair of binoculars can become mis-collimated. Many makes of binoculars have setscrews on each barrel to adjust the prisms and bring the images back into alignment.
Instructions
1. Take the binoculars outside and locate an object that is more than 100 yards away and composed of straight vertical and horizontal lines. A house or other structure is a good choice.
2. Focus the binoculars on the structure.
3. Check horizontal collimation by locating a vertical line in the structure such as the edge of a wall or window frame. Alternate your view about once per second by gently closing one eye at a time. Look for any impression of movement in the vertical line as you shift viewing eyes. Some small movement is normal. Excessive vertical movement --- or any apparent vertical movement in the vertical line -- means adjustment is required.
4. To check vertical collimation choose a horizontal line such as a roof line or gutter. Move your eyes about four inches away from the binocular lenses while continuing to observe the horizontal line. Look for any disparity in the horizontal line from one lens to the other. Vertical mis-collimation shows up as a slight difference in the vertical position of horizontal lines.
5. Locate the prism tilt adjustment setscrew on each barrel of the binoculars. If the binoculars have a rubber weatherproof covering it may be necessary to peel the covering back to find the setscrews.
6. Adjust the prism tilt setscrews with a small jeweler's screwdriver. Turning the setscrew clockwise on the right side moves the image to the left and down. Turning the setscrew counterclockwise on the right side moves the image to the right and up. On the left side, turning the setscrew clockwise moves the image to the right and down. Turning the setscrew counterclockwise moves the image to the left and up.
7. Make adjustments in small increments, frequently evaluating the images using the above procedure until they are aligned. Often, minor vertical mis-collimation can be corrected by adjusting only one side of the binoculars.
Tags: moves image, horizontal line, vertical line, binoculars have, down Turning
