[Aavso-photometry] Atmospheric extinction questions

[Gary Walker]

Hello Jim;

You will see a difference.? From Bruce Gary's book on ExoPlanet Light Curves, for a Type A2, 8000K and a type K3, 4500K, you will see approximately 6 millimags per air mass.? Other differences accordingly.? How much are you seeing?


Thanks

Clear Skies
Gary Walker
Maria Mitchell Observatory
4 Vestal Street
Nantucket, Mass 02554


-----Original Message-----
From: Jim Roe <jroe at jamesroe.com>
To: Aavso-Photometry <aavso-photometry at mira.aavso.org>
Sent: Tue, 13 May 2008 9:51 pm
Subject: [Aavso-photometry] Atmospheric extinction questions



I'm doing differential photometry.  Ie, my comp stars are on the same 
image as my target and, usually only a few arc minutes away.  Ergo, I 
expect delta X to be zero.  According to Hall & Genet, the second order 
extinction coefficient in V band is essentially zero.  So, should I see 
a brightening of my target as it rises from a low elevation (High air 
mass) to a high elevation (low air mass) (in V)?  The B-V values of the 
target and comp star are very close, too.

Jim Roe [ROE]
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