On the polar finder, tonight I had a go at collimating it. My conclusion, I think I messed it up beyond repair.
To cut a long story short, I can't keep the main barrel on the correct optical axis relative to the mount.
I now know more about how it is built than I ever wanted to know... on the tip is a cemented doublet. It fell out as I disassembled it, and thankfully one side was dirty enough for me to tell it was the one facing outside!
The main barrel is a plastic tube with thread on both ends, the other end screws into the section holding the image overlay and light source. A mistake I made in the past is that there is a screw holding the barrel in place. When I last dropped it, I unscrewed and rescrewed it in without touching that screw, which stripped off a lot of thread on the plastic barrel. The thread on both ends of the barrel appears the same, but even if I reverse it to use the other good end, it screws in very loosely that even with the screw tightened, it wobbles.
Inside the assembly is the insert which has the overlay. That is held in place with three screws which you can adjust to collimate it, assuming you didn't mess up the rest as badly as I did. Finally is the rear section holding a lens assembly of relatively short focal length. This overall seems to produce a basic telescope with inverting image. I think the image overlay should sit at the common focal point in order for everything to be in focus.
I think right now, my best bet might be to try replacing the plastic barrel with something else more sturdy, but I'd need to get the thread and diameter exact. That'll be tough I think. The alternative is to buy a replacement polar finder. I wouldn't get the same one again, but I'm not sure if any other model would be mechanically compatible or would otherwise be easily modified as such.
_________________Canon DSLRs: 7D2, 7D1, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 85/1.8, 135/2+SF, 70-300L, 100-400L, 100L, MP-E 65, EF-S 10-18, 15-85
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 50/1.4A, 150 macro, 120-300 f/2.8 OS
Compacts: Sony HX9V, Fuji X100.