@scanlime i got it to work! the parts i was looking at were not threaded, but it turns out one of them came apart into two parts, which threaded together. and the glass had to be clamped between them!
i had to look at the other lens i had to figure out the right orientation, though. I think it's back together and working~!
the mastodon instance at cybre.space is retired
see the end-of-life plan for details: https://cybre.space/~chr/cybre-space-eol