Re: shutter

[Tom Droege <droege@FNAL.GOV>]

Arne and all,

My speed assumption on the Mark IV is that no exposure would be less than
100 seconds.  To get more sensitivity than the Mark III, we need to run at
of order 1000 seconds.  I am not trying to build an instrument that does 
everything.  I priced large fast shutters at prices similar to the CCD.  
Too much for me.

Hmmmm!  How does a shutter really affect the exposure when it is an opening
slit?  I recall focal plane shutters work by driving a slit across the film
plane.

Yep, I thought about the "curtain shutter", but it just took too much space.

In general, I expect timed operations to be done by the PC.  One would only
do "limit of speed" operations in the stamp.  While I am trying to include
in the design the ability to run one camera at a time, I am really planning
on exposing and reading them out together.  

Sigh!  OK, the next version of the mount will reach the Pole.  I will shoot
for 135 degrees in declination.  But I expect to use the part near the 
horizon as a built in flat field screen.  It seems to me that there is 
plenty of science to be had between the Pole and the Equator.    

My idea is to build a bunch of cameras and put one in the south, or at the
equator to see the galactic bulge.  I have long fought "escallating greed"
in the design of experiments.  It is this sort of thing that gets us a 
Sloan that can't be built.  So I will fight to keep the design simple and
limited.  But I do listen, and will add all that I can for a good reason.

Tom Droege