Re: Clear Sky Detector

[Arne Henden <aah@nofs.navy.mil>]

LOTIS used "fog flats" due to their California location.
That seemed to work fairly well for them with their 7.5degree
field.  Individual cloud flats are likely to have spatial
structure, but an average of many should be ok.  Note, however,
that setting exposure times can be painful; the light source
is typically urban skyglow, which does not look very blackbody-like;
and you have to watch out for rain/snow. :-(
   Still, cloud flats are another check to see if the lightbox
flats are correct.
Arne

Michael Koppelman wrote:
> You are the man, Tom.
> 
> Any chance that cloud cover would make for good flat fields?
> 
> Michael Koppelman
> 
> 
> On Tuesday, February 11, 2003, at 11:41 AM, Tom Droege wrote:
> 
>> Last night was almost solid clouds.  I set up the Mark IV so that it 
>> would take darks when the sky was cloudy and object frames when the 
>> Clear Sky Detector said it was OK.  The result was that the detector 
>> found 3 patches of clear sky out of about 150 images.  Since only one 
>> of these was really clear, I think I have it set about right.
>>
>> Next comes the Day/Night detector.  I found a Panasonic device that 
>> might do the trick.  The PNA4603H.  I ordered 10 at $3.51 each.  We 
>> shall see.
>>
>> I will then just turn on at dusk and let the Mark IV decide what to do.
>>
>> For those that have asked, the TEC I am using is a Melcor 
>> CP1.0-127-05L.  If I were designing from scratch rather than taking a 
>> device out of a cabinet, I would use one with longer junctions.  For 
>> this purpose I would pick one with the largest number of junctions.  
>> The signal is of order a millivolt so a low offset amplifier is > needed.
>>
>> Edison is supposed to have said "Invention is having an idea and a lot 
>> of junk".  I do have a wonderful collection of junk.
> 
> 
> 
> 
>