A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2016 Apr 9, 06:50 -0400
It just occurred to me I may be barking up the wrong tree.
From your original problem statement, I cannot determine if the smear occurs only with the telescope or appears without it as well.
If it's only with the telescope, then a lens may be off axis.
If it appears without the telescope and only with the mirrors, then it could also be a reflection off of an internal surface, other than the mirrors. Like a shade frame for example.
Any competent machine shop can make just about any screw to any thread. I've had it done. It is not cheap. One manufacturer here in the US was fond of making oddball threads in the 1800's to make sure you could only buy parts from themselves. It is a nightmare because you simply can not source those screws today. That is, without getting them made.
As to the resilvering, I've had that done too. That's actually not so expensive at all. I had both the index and horizon mirrors done. Came out beautifully.
As to your phantom, you may have missed my point. One of the lenses may be slightly off axis. Wouldn't take much. That's why you should take the lenses out (clean them) and put them back. It's to reseat them and get them back on axis. It could be nothing more than an eyelash at the edge of a lens seat.
One other venue for parts is to simply (ha!) buy another box sextant of the same type for parts. Use two to make one.