[SQM] Lunar eclipse, a calibration opportunity

Jan Hollan jhollan at amper.ped.muni.cz
Tue Feb 19 10:41:23 UTC 2008

Sorry for the bad links, instead of just amper, amper.ped.muni.cz is to be
used as a server name; these are the complete addresses:


It's corrected in my archive,
 but it remains wrong in the SQM archive of course.

I admit that to bring the SQM measurement to the maximum use, not to speak
about digital camera measurement is no easy thing, and that it's further
complicated by the eclipse.

However, sky luminance under full Moon (outside eclipse) gives a good
proxy for zenith extinction, and if the luminances would be the same at
two little-polluted places with the same sinus of angular height of Moon,
so would be the transparency of the air. Any pronounced difference between
the sky luminances during the eclipse would be then due to artificial
sources of light. This way, light pollution at these places can be
compared directly, even without measuring the extinction quantitatively.
Of course, this would not hold for those city centres, where even full
Moon is not a dominant source of sky luminance...

(now I see another error in my yesterday's posting, I don't think the
ratio of moonlight during and outside the eclipse is 5e6, it should be an
inverse of 5e-6, ie 2e5, taking it from the caption to my 2004


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