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Hello,
There are a number of factors that can affect the magnitudes.  These should all be identifiable from the help description.  The magnitude depends on the zero point (obviously), the exposure time, the area of the aperture, and the sky.  The area depends on the scale units specified.  If you want me to look at your parameters send me the result of cl> lpar phot datapars photpars centerpars fitskyparsYours,
Frank Valdes
On Nov 12, 2005, at 8:04 AM, Hu Juei-Hwa wrote:
[quote:47b89957d3]Dear Sir,
 
I have a problem about the output mag. values of the digiphotx package.
 
Recently, I always get the mag. values larger than before in both apphot and daophot packages. The zero point is the same before and now.
I set the parameters follow the cookbook, A Reference Guide to the IRAF/DAOPHOT Package, by Lindsey E. Davis,1994. 
In the same image, I get ~2.5 mag. larger than before. I've checked most of the stars in the image.
 
About one month ago, it happened once. I checked the parameters and reset them. The problem was gone and I can get the "normal" mag. values.
In these days, it happens again. After I check and reset all parameters (I did what I did last time), the problem is still there.
 
I have no idea how I can get back the normal mag. values.
My OS system is Fedora Core 3. The vision of IRAF is 2.12.2.
Do you know what causes the problem? any parameters I missed to check?? Does anyone has the problem??
 
Thank for your help.
 
Regards,
 
Hu Juei-Hwa
 
 
--
Hu Juei-Hwa
Institute of Astronomy,
National Central University, Taiwan
TEL +886-3-4227151 ext 65969
FAX +886-3-4262304
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