SFS: Subs taken through cloud vs clear, dark sky?

[Terry Danks]

Last night I know there was thin, high cirrus cloud about. When I checked the subs against those taken another night, when it was clear, I expected to see figures in the SFS that would allow me to distinguish "bad" subs, i.e., those taken through the cloud, from the "good" subs, taken in a clear sky.
I saw nothing in the FWHM, Ecc, or SNR figures that pointed to the "cloudy subs" being better, or worse than the "clear" subs.
This does not seem logical and I am puzzled.
Comments?

[John_Gill]

Hi,

I have had subs that have had similar SNR, Eccentricity, FWHM, etc. etc. Except one sub that has a large spike in the SNR.  When looking carefully at that sub I found that it was "brighter" because of thin cloud hence the SNR spike. Perhaps the seeing conditions and the clouds even things out. 

space is not black
John

[mschuster]

Yes, things like clouds, gradients, and dew sometimes cause excessively large "signal" measurements. Can you place one "good" and one "bad" sub in DropBox? I will take a look. Also, as a workaround, you might try an integration with no weighting, no output normalization, and no rejection normalization. Although this may not sound like a good idea, and the results may not look like your reference sub, the integrated results from an SNR perspectively often will be excellent.

Mike