Shiming a Finder

[GCoyote]

So the mount for the 5x24 finder on my small newt only has three adjustment screws toward the front of its mount. That leaves a bit of play at the rear and some looseness during use. It's such a small amount that I folded a post-it note in half and used that to shim it into position.

Is there a better/easier way to do that? At least easier than drilling and tapping three more holes?

[JayTee]

Pictures would certainly help with getting a useful reply.

Cheers,
JT

[Lady Fraktor]

Sometimes that is what is required, I have a 9x50 finder that is the same way and requires a shim to get enough movement range.

[GCoyote]

Pictures would certainly help with getting a useful reply.

Cheers,
JT

Yeah, I need to think of these things before 11 pm.

[JayTee]

Ah-ha, I see.

In the past, I have used a piece of black electrical tape to go all the way around the finder scope tube to act as a shim. On a lighter colored tube it kind of looks like a "racing" stripe!

JT

[Ruud]

I think the eyepiece should be on the same side as the adjustment screws. Like below. Maybe it fits better this way.

[GCoyote]

I think the eyepiece should be on the same side as the adjustment screws. Like below. Maybe it fits better this way.

...

It's on the top end of a Newtonian so there's no room to reverse it. My face would be in the elevation control.

[Lady Fraktor]

The screws should be more centered on the tube or towards the rear of the tube for more adjustment of the lens, in this position all of the movement will be at the eye end.

[Ruud]

I mean this:

animated-Seeker-76.gif (47.51 KiB) Viewed 1886 times

[GCoyote]

Probably my question wasn't clear. Placement is correct per the instructions and the finder's mount is firmly attached to the OTA. No problem there. (Also more convenient when you consider where the eyepiece is.)

It's a little hard to see because of the paint job but the total angular deflection of the finder is limited by the adjusting screws at one end of its receiver and the slightly smaller opening at the opposite end. I have enough deflection available to align the finder to the OTA. The only problem was the looseness of the finder scope in its receiver which allowed it to wobble a bit during an observing session. Shimming seems to be the agreed upon solution.

Thank you everyone.

[gregl]

I've got one wherein the back end is "shimmed" with an o-ring that wraps around the scope and thus takes up the space between the scope body and the mount. Check yours to see if that's the case. If so you might be able to get an o-ring with slightly thicker rubber "string." Here's a link to some data on o-rings: https://www.mcmaster.com/o-rings/oil-re ... o-rings-8/

And now that I think about it, even if yours doesn't have the o-ring, putting one in there would shim it. Tape will work but the adhesive on some tape will seep out in warm weather or over time.

[GCoyote]

Nope, no O-ring. It's okay, the paper/electrical tape shim is doing the job.

Thanks