[Aavso-photometry] Effect of aperture size

[Tom Krajci]

Jim,

Any comments about star image width/PSF?  Perhaps a few graphics posted 
somewhere?  Screen grabs of star profiles?  What does it look like when 
your aperture and annulus are placed over the star(s)?

Do you defocus?  What's your pixel size/f.l./sampling?

Thanks in advance,
Tom

-- 
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Tom Krajci
Cloudcroft, New Mexico
http://picasaweb.google.com/tom.krajci

http://overton2.tamu.edu/aset/krajci/

Center for Backyard Astrophysics (CBA)
http://cbastro.org/ CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
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Message: 5

Date: Thu, 17 Apr 2008 08:07:35 -0500
From: Jim Roe <jroe at jamesroe.com>
Subject: [Aavso-photometry] Effect of aperture size
To: Aavso-Photometry <aavso-photometry at mira.aavso.org>
Message-ID: <48074B97.9000400 at jamesroe.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I measured a transit of GJ436 in B.  The light curve was beautiful 
(IMHO), see

<http://brucegary.net/AXA/GJ436/gj436.htm#Light_Curves>

BUT, there was a discrepancy in the depth of the transit of some 3 mmag 
(compared to earlier results by lots of observers) so I re-measured the 
images using different aperture sizes (I use MaximDL)....

Jim Roe [ROE]