First Mark IVb Camera

[Tom Droege <droege@wwa.com>]

The first Mark IVb camera has rolled off the assembly line.  I took lots of
pictures and should have them in a few days to show and tell.

It is now in test.  The first thing I did was to try the thermoelectric
cooler.  I was able to get about 55 C below the water temperature.  It
should be practical to operate at -25 C which is cold enough with our sky
background to run in non-MPP mode.  This gets 4x the dynamic range of MPP
mode for the 242A CCD chip.  

Most things fit together as planned.  It is a very tight package.  All of
the space inside the head is filled with wire or parts.  

It took two pretty full days to put this first unit together.  This will
improve a little when I get all the shutter parts cut out professionally.
I will get pretty sick of the work by the time I build 40 of these beastes.
  Each version of the shutter works a little better.   The next version
should reduce the light leaks to near zero.

Tom Droege