Note on turning filter wheels

It was discovered the hard way in mid January that there is nothing
to prevent the filter wheel shafts from being removed from the dewar.
Pulling them out a quarter inch allows warm moist air from the
room to enter the dewar's vacuum cavity and contact the cold surfaces.  

Push the shafts in slightly as you rotate so they do not drift out.

The west knob is harder to turn when in the range of 1 to 2 o'clock
than it is at other  positions.
The east knob was not tested as carefully throughout its rotation.

Marc Lacasse