http://weather.uwyo.edu/upperair/sounding.html This is the like to the sounding data that is collected twice a day. It's my primary source for view condition information. DT ________________________________ From: Tyler Allred <tyler@allred-astro.com> To: 'Utah Astronomy' <utah-astronomy@mailman.xmission.com> Sent: Friday, September 28, 2012 6:37 PM Subject: Re: [Utah-astronomy] Dry Daniel, Interesting thoughts on the seeing conditions this year. I can attest to the bad seeing all summer. It has really cramped my style! Tyler -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of daniel turner Sent: Friday, September 28, 2012 12:22 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Dry A thin layer of cirrus cloud will act like a blanket and trap the heat on the ground so that the temperature doesn't fall below the dewpoint. This layer is often hard to even detect unless your trying to view galaxies through it. The moon, Jupiter, Saturn, Mars, and bright double stars can burn through it but detail in M101 or M97 just disapears. Data collecting like transit searches are protected by callibration against adjacent stars in the same field. Ground level dew is only part of the problem. I regularly view the U of Wyoming's sounding map website. It tells me the total water in the air all the way up. When less than 10cm the conditions are good. This year we have been consistantly of 20cm for weeks at a time. When it's this high you will always find a layer of air somewhere in the sky with a RH above 50%. That's the cirrus layer that kills the deep space viewing. DT _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options". _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options".