Re: [APML] Sky fog

[Aplanatic@aol.com]

Tom,

> I do have an ST-4, but the problem is that I image from my back
>  patio...streetlights nearby.  There is plenty of ambient light on trees and
>  buildings that would spoil the measurement of an ST-4 just pointed skyward.
>  
>  What if I rigged up some sort of light shield/snoot on the ST-4 to 
eliminate
>  my ambient light problem...could I still make useful measurements for you?

The idea behind using the ST-4 to measure sky glow is that the CCD, with its 
nosepiece, looks into a region of sky about 60 degrees in diameter.  If you 
can add a shield in such a fashion that it does not change or reduce this 
angle then the shield will not affect the measurement.  As long as the CCD 
can't see direct or reflected light from the streetlamps then I think that 
the measurement should still be valid.  Even though the shield does not 
reduce the solid angle seen by the CCD, it may be useful in reducing 
reflected light from the inside of the barrel.  If you try it, you'll have to 
estimate the effect of the streetlights on the measurement, perhaps by some 
clever experiments.

Thanks,

Dave Rowe

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