Telescope Reviews: Aligning Fujinon

Hi All,
I tweaked the conditional alignment on my bought-used 7x50 FMT-SX, and it was so much fun that I thought I'd describe the procedure for others. Most of it will apply to any eccentric-ring adjustment.

1)Mount the bino, sight a distant object, and determine the direction of the error. I don't like the method of backing off a few inches, because I found the result to be sensitive to eye position. I prefer to look into the bino with one objective covered, quickly uncover, and notice where that eye sees the image relative to the first eye.

2)Dismount, and take to a well-lit work area. Determine the orientations of the eccentric ring objective mounts by looking directly at the front, and finding the narrow crecent-shaped profiles of the part of the ring that the lens if farthest from. Use masking tape on the outside of the barrel to mark these positions.

3)Plan the adjustment, based on the observed alignment error and the ring orientation. The direction of motion is analagous to what happens in normal usage: if you point the bino up, the object viewed appears to move down in the field of view. So, rotate the objective so as to move the lens opposite to the way you want the image to move.

4) Remove the rubber cover from the objective(s) you plan to adjust.

5) Remove the outer retainer ring. I made a tool from a stiff piece of 1/16-inch thick metal, cut to length to span across the ring, and filed down at the ends to fit snugly into the slots. Protect the lens with a cardboard circle. Use a good bit of force to keep the tool seated as you turn counterclockwise to loosen and remove the ring.

6) Lift out the tabbed rotation-proof washer and the spacer underneath.

7) You will now see that the the lens is encircled by three rings. The middle of these rings provides the adjustment. Put a bit of masking tape on the end of the barrel, and mark the location of one of the adjustment slots. For making the adjustment, I used a machinist's compass to span the ring. The two points nestled snugly into the ring's adjustment slots, constrained from motion inside or outside by the adjacent rings. Again use careful force.

8) Make a small adjustment, about 1mm of motion of the slots, go back to the mount, view the object, assess what you've done, and continue until you see no error.

9) Put her back together, grab a cold one, and say to yourself "anything that can be adjusted with a jeweler's screwdriver is not gonna stay for long".

Ron