The moon was about to set just after midnight last night and I decided that conditions were ideal for a PEP transformation calibration sequence (only practical to do when skies are clear, steady and transparent). The dry north winds minimized the risk of dew formation on the scope objective during the couple of hours and as a bonus, it was too cool for most of the mosquitoes at my place (north shore of Lake Ontario). However I noticed a steadily declining trend in the photometer output of the calibration stars (battery was good) and realized that this didn't look good (variable transparency and extinction is a no-no for the transformation calibration sequence), but continued anyway to finish the set of observations. This morning, it's obvious at a glance what happened, since the sky is a hazy blue, not what we get with north winds and dry air, but similar to smoky skies.
I posted a few images showing the smoke plume at the blog:
windsandcloudsblog121.blogspot.ca
Too bad I don't have a brain, otherwise I would have checked the GOES satellite aerosol loop http://www.ssd.noaa.gov/PS/FIRE/GASP/loop.html before starting and decided that it was obvious that smoke was on the doorstep.
Frank
DFR
Hi Frank.
I was outside Sunday before dawn doing visual estimates of a few stars, on the outskirts of Indianapolis. It was very clear, but my horizons seemed more murky and lit-up than usual. I wasn't sure why they seemed this way until I read your post, and now I'm thinking that some of this smoke also came down my way! Good luck on your PEP calibration. I have tried doing this several times this summer but the issue seems to be getting the telescope to track the sky long enough for the target star to stay in that illuminated reticle on my SSP-3.
Paul
ZPA
Hi Paul,
Thanks for your observation about the murky-looking sky. It seems reasonable that some of the smoke was over Indiana, since the airflow was across Lake Ontario and then southwestward over Indiana. Your skies normally ought to have been clean and dry with winds from the E or NE, but the NOAA-HMS smoke analysis image for July 30 shows that some smoke was analyzed over central Indiana. I attached the chart below. Anyway it illustrates one of the hassles of trying to do careful photometry during the wildfire smoke season!
Frank