[AZ-Observing] Sky at Anderson Mesa
- From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 6 Oct 2005 15:45:37 -0700 (MST)
As I've mentioned on this list previously, I've been making measurements
with one of the SQM sky-brightness meters over the last several weeks.
Last night at Anderson Mesa was what I would call a 'typical' dry-season
photometric night strictly from the visual impression. The SQM numbers were
also as consistent as one could expect from a simple device like this:
UT Date hhmm LST site mu pv dp remarks
(mm) (C)
20051006 0300 2030 Mesa 21.38 9 -3
20051006 0400 2130 Mesa 21.39 9 -3
20051006 0500 2230 Mesa 21.39 9 -2
20051006 0600 2330 Mesa 21.40 9 -3
20051006 0700 0030 Mesa 21.39 9 -3
20051006 0800 0130 Mesa 21.37 9 -3
20051006 0900 0230 Mesa 21.40 9 -4
20051006 1000 0330 Mesa 21.40 9 -2
20051006 1100 0430 Mesa 21.41 9 -2 pv = 6mm at 12h UT
...where the 'mu' value is the SQM reading in magnitudes per square arcsecond.
Rough modelling indicates this 'all-sky' value is about 0.3 mag brighter than
one would measure for a small star-free spot at the zenith in the V band.
The total-column precipitable water-vapor dropped from 9mm for the 5pm sounding
to 6mm in the 5am sounding; local dew-point was pretty stable.
I've also mentioned in the past getting these particularly inspiring
short views of the sky from an open area not far from the telescope compound.
I stopped at this spot this morning (about 4:45a) and the overall view of the
sky was similar, trending in me to basic stupefaction (to quote the old
Firesign Theatre bit: "I was seized by a transport of scientific rapture"),
with blazing bright zodiacal light in Leo and Cancer, winter Milky Way,
windless dead silence, etc etc. Obviously this is largely psychological,
but now I have numbers to go with it!
\Brian
P.S.: A reminder that the nightly cloudiness and sky-brightness data are
tabluated at the Lowell Web site starting at:
http://www.lowell.edu/cgi-bin/www/clouds/clouds.cgi
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