It finally stopped the light snow so I could roll off the roof and work
without being hunched over. I found the cold contracts the stainless
steel (I think) screw that acts as the axle for the filter wheel. It
goes through a plastic (teflon?) bearing. While it turned fine when I
last had the filter wheel out (September) it now turned real stiff at
the Luminescence filter position. The rest of its rotation was free. I
loosened it about an eighth of a turn and it now turns freely. Then
after the camera was reassembled, at 10 degrees so my fingers were not
happy and as the clouds rolled back in I got a couple flats taken
rotating the filter wheel one way then the other way back to the
luminescence position. Now instead of 3D looking donuts I got a flat
gray image when I used one to flatten the other. Before, even coming in
from the same side I'd get those 3D looking donuts from misalignment.

It appears that screw just contracted too much and pinched the bearing
slightly at the luminescence filter position.

The rubber "O" ring showed no sign of temperature problems seeming to be
about the same as at much warmer temperatures.

Now I'll see what happens when it gets even colder. I may need to
loosen the screw some more but didn't want to loosen it so much the
wheel wobbled or again there'd be an alignment problem.

Snowflakes are starting in again so I doubt I'll be watching the Moon
and Pleiades tonight.

Rick

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Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".