Let me point out that I have added a new feature to the "Weekly Plot" at the bottom of my "Weather Plots" WWW page: http://www.astro.washington.edu/deutsch/apoinfo/cloudscan/weatherplot.html The mean and median 1.0 micron dust counts for the past 7 nights (yes, nighttime only!) are printed at the top of this weekly data plot. For example, today the mean is about 5500 particles per cubic foot (note that this unit is 10x the raw numbers seen from the instrument!). Perhaps a strategy of closing the telescope when the the observed value of dust counts is some factor of the mean for the past week would be more appropriate than closing at an arbitrary value (16000 PpCF is the current value, as I understand it, which is ~3x last week's mean). For example, when the dust counts increase to 10x the mean for the past 7 nights (and one estimates that a night is 10 hours long, and that the dust accumulation rate is proportional to the dust density) one might think that the mirror is saved from a night's worth of contamination for every hour that the dome remains closed. At some point in the near future, I hope to investigate the situation a little more closely and/or provide a tidy dataset for other folks to play with. However, one item which might be helpful to stir into a simulation for addressing this problem is the exact times that the dome is open (and if not, why not!). Does someone have easy access to a database furnishing this information, and if not, maybe we ought to keep one. Eric ---------------------------------------------------------------------- Eric Deutsch email: deutsch@astro.washington.edu Department of Astronomy Voice: (206) 616-2788 University of Washington FAX: (206) 685-0403 Box 351580 WWW: http://www.astro.washington.edu/deutsch/ Seattle, WA 98195-1580 Physics/Astronomy Bldg., Room B356F APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 185 in the apo35-general archive. You can find APO the archive on http://www.astro.princeton.edu/APO/apo35-general/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-general@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO