[Aavso-photometry] Measuring aperture

[Gary Walker]

Hello Barbara

Your question has been answered correctly as far as I know.  I just 
wanted to comment that Maxim/DL does manage this for you, from what I 
can see in using it.  If I do a PT run, and then discover that I want 
to change the aperture of say the ref star, then it changes is for the 
object and the check stars, in all images and recomputes the 
magnitudes.  I do not know how this is handled by other softwares.  I 
use version 4.61.

Thanks

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


-----Original Message-----
From: Barbara G. Harris <barbharris1 at hughes.net>
To: aavso-photometry at mira.aavso.org
Sent: Sat, 17 Jan 2009 3:20 pm
Subject: [Aavso-photometry] Measuring aperture

I have been doing CCD photometry for a few years but I have been getting
back to basics and digging into how my program (mostly Maxim, but also 
use
AIP4Win) calculates magnitudes.  I have a question that is probably 
pretty
basic but I would like to have it confirmed:  When measuring the comp,
check, and variable do you have to use the same size aperture and 
annulus
for each star in the field or can you adjust the diameters because of 
field
crowding?  I have made sure to always use the same size and I assume 
that is
why it is recommended to use stars of similar magnitudes.



Barbara

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