Path TR303 transit adjustment

Hi all,
Does anyone know how to turn the whole reticle on an old transit? My crosshairs are leaning slightly to the right so the reticle needs to be turned but I am not sure which of the screws to loosen to do this. Can someone help?

roydaniel --

My recollection -- from decades ago -- is that the Path TR303 has a sheetmetal "trim ring" cover over the reticle adjustment screws. The cover diameter pretty much matches the telescope housing diameter, and if it's not corroded in place, can be removed by grasping it with the fingers and turning it off. I think it comes off over the eyepiece lens assembly, but if it doesn't, the eyepiece lens unscrews from the end of the telescope barrel . . . and I recommend grasping the knurled ring that's right up against the body of the telescope -- using padded-jaw pliers if necessary -- and NOT the knurled ring around the eyepiece lens that's used to adjust reticle focus.

Once you have the reticle-ring cover off, you'll see four reticle-adjustment screws, one each at the top, bottom, right, and left sides of the telescope barrel. These screws are usually capstan-headed, and their adjustment takes a "pin wrench". If you don't have a factory pin wrench, the shank of a twist drill that barely slides into the cross-hole in the screw head makes a reasonable substitute. I'll recommend against using a hex key (commonly called an Allen Wrench), which usually boogers-up the screw head.

Some instrument makers did use Allen-head screws -- sometimes with the usual cylindrical head, sometimes with flat heads -- in place of the capstan-head screws if / when the reticle ring was covered by a trim ring. These obviously require a correctly-sized hex key.

The reticle-adjustment screws usually have arced rectangular washers underneath them that provide a bit of spring to protect against over-tightening the adjustment screws, and to cover slots in the telescope barrel that allow the reticle, which is suspended within the telescope by the four reticle-adjustment screws, to be adjusted up-or-down (or right-or-left) by slight loosening of one of the top-and-bottom (or right-and-left) screw pair while tightening the other of the pair the same amount.

To "clock" the reticle, two adjacent reticle-adjustment screws need to be slackened to relieve ALMOST all the tension in the screws, and then one of the screw heads is gently tapped to rotate the whole assembly of reticle, reticle ring, four screws, and four arced washers in the telescope.

After the adjustment is made, the screws that were loosened need to be retightened, and the reticle adjusted for "horizontal collimation", which is jargon for the telescope line of sight needs to be set perpendicular to the trunnion axis-of-rotation.

The best way to evaluate reticle "clocking" is to point the telescope so that the top of the vertical crosshair is on a clearly defined point -- being sure that the instrument's horizontal motions are securely clamped -- and then plunge the telescope to see if the vertical hair stays on that point.

John

Thanks John, I will try that and see if I can mess something up. I could send you a picture of the exposed screws if you like to make sure I get it right.
Roy

Roy --

I swing through this board only occasionally, which you may have figured out by now.

If you still haven't fixed the orientation of your TR303's reticle, and want me to take a look at a photo before you start working on it, please post the photo(s) on Photobucket, Flickr, or one of the other photo-hosting sites, and post a link back here.

I'll try to make a point of checking here every couple of days until you respond.

John