Clear Sky Detector

[Tom Droege <tdroege2@earthlink.net>]

The Mark II Clear and Dark Sky Detector is now undergoing tests.  The 
scheme is such that the detector only puts out a positive signal if the sky 
is dark and clear.  First results are promising.  It is quite 
directional.  A soldering iron held in front of the tube sets it off to - 
full scale as it is supposed to do.  It does not detect the soldering iron 
off axis.  The tube is about 1.5" in diameter and 12" long.  This gives an 
opening angle in the 7 degree range.  Not a bad match for the 4 degree Mark IV.

The light detector that I bought seems to work just fine.  I shall have to 
wait to see when it says it is dark.  This is not intended to be a "dark 
enough to take images" detector.  It will probably say it is dark well 
before sunset, but we will have to wait and see.  I should get it on the 
telescope tomorrow.

Meanwhile I am using the Mark I every night for operation.  If the sky is 
not clear, the program takes a dark frame.  At the moment it is sitting at 
-10 volts because the sun is shining on it.  Once the sun goes past, it 
will return to the +1 volt that indicates a clear sky since I see blue out 
the window.

I have most of a write up completed, and a schematic has been drawn.  Just 
a little clean up work is needed to get a TN out to show you how to do it.

Tom Droege