Re: Sky Clarity

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

There is no official fits header keyword for seeing or sky
transparancy.  You are free to choose names of your own making.
   Cloud monitors are nice, but are not foolproof.  There are
worlds of difference between cirrus, stratus, cumulus and fog.
You also have to come up with a quality factor and then a threshold
on that quality factor.  It is much easier to just take the data
and then determine after the fact whether a night was photometric.
If a human is in the data-taking loop, that human can often decide
(without quantifiable factors) whether he/she thinks the night is
photometric, but with an automatic system like TASS, just wait and
look at the data.  TOMxx should not be doing all-sky measures normally;
Chicago is a poor photometric site except for the Fall.
Arne

Tom Droege wrote:
> Arne and anyone else that wants to answer,
> 
> I am working on a "Sky Clarity" detector.  The idea is to measure the 
> radiation loss to free space.  So far the device looks promising.
> 
> My idea is that for tass telescopes this might be a good way to select 
> the best photometric nights.  Big telescopes would probably also want 
> good "seeing", but I doubt that "seeing" makes much difference for tass 
> measurements.  What I hope to measure is how much stuff is between the 
> telescope and space.
> 
> I would like to put this measure in the .fits header.
> 
> Is there some "official" fits header term to use?
> 
> Tom Droege
> 
> 
>