Fwd: a problem about the phot

Francisco Valdes wrote on Nov 28, 2005

From: "93249003-Hu Ruei-Hua" <d939003@mail.astro.ncu.edu.tw ([email]d939003@mail.astro.ncu.edu.tw[/email])>
Date: November 23, 2005 9:09:18 PM MST
To: Frank Valdes <valdes@noao.edu ([email]valdes@noao.edu[/email])>
Subject: Re: a problem about the phot

Dear Sir,

Thank you for your reply. I've found the parameter that make the magnitudes 
strange. It is the exposure time. I made a embarrassing mistake. ^^
Thank you again and have a nice day!!!

Bests,

Hu Juei-Hwa

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---------- Original Message -----------
From: Frank Valdes <valdes@noao.edu ([email]valdes@noao.edu[/email])>
To: Hu Juei-Hwa <d939003@astro.ncu.edu.tw ([email]d939003@astro.ncu.edu.tw[/email])>
Sent: Wed, 23 Nov 2005 16:05:19 -0700
Subject: Re: a problem about the phot

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 fitskypars

Yours,
Frank Valdes

On Nov 12, 2005, at 8:04 AM, Hu Juei-Hwa wrote:

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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Last post on Nov 28, 2005