Phot task Mag & Mag_err outputs = 0 at random
Don Schumacher, Jr. wrote on Feb 05, 2011
My question is if anyone else has ever noticed this problem in their output files from the phot task. Below is an example of where it occurred. As you can see there are 4 stars each with a flux, mag, and mag_err. Each row is from one image. The problem lies in the Mag and Mag_err that IRAF calculated for the star C3 in the 2-4 images:
[size=9:f5274ce367]Target Flux Target Mag Target Mag_err C1 Flux C1 Mag C1 Mag_err C2 Flux C2 Mag C2 Mag_err C3 Flux C3 Mag C3 Mag_err
51387 19.416 0.009 73946 19.021 0.006 47821 19.494 0.008 91159 18.793 0.005
53613 19.370 0.007 75700 18.995 0.005 49536 19.456 0.007 89087 0.000 0.000
54978 19.342 0.008 77740 18.966 0.005 49523 19.456 0.007 90791 0.000 0.000
55301 19.336 0.007 77885 18.964 0.005 50643 19.432 0.007 91397 0.000 0.000
59633 19.254 0.006 79008 18.949 0.005 51745 19.408 0.007 97540 18.720 0.004
60311 19.242 0.006 79437 18.943 0.005 51659 19.410 0.007 98766 18.706 0.004
[/size:f5274ce367]
Does anyone know why phot would calculate the mag and mag_err fine for all the other stars, and the C3 star in other images, but then mess it up apparently at random in those three spots? The star still had a clear flux and the problem can't be in the sky count since it didn't affect other stars in the same images.
I would be interested in any insight on this matter.
For now I will just have to go in and use the formulas IRAF uses by hand for those spots which is just a bit annoying.
[size=9:f5274ce367]Target Flux Target Mag Target Mag_err C1 Flux C1 Mag C1 Mag_err C2 Flux C2 Mag C2 Mag_err C3 Flux C3 Mag C3 Mag_err
51387 19.416 0.009 73946 19.021 0.006 47821 19.494 0.008 91159 18.793 0.005
53613 19.370 0.007 75700 18.995 0.005 49536 19.456 0.007 89087 0.000 0.000
54978 19.342 0.008 77740 18.966 0.005 49523 19.456 0.007 90791 0.000 0.000
55301 19.336 0.007 77885 18.964 0.005 50643 19.432 0.007 91397 0.000 0.000
59633 19.254 0.006 79008 18.949 0.005 51745 19.408 0.007 97540 18.720 0.004
60311 19.242 0.006 79437 18.943 0.005 51659 19.410 0.007 98766 18.706 0.004
[/size:f5274ce367]
Does anyone know why phot would calculate the mag and mag_err fine for all the other stars, and the C3 star in other images, but then mess it up apparently at random in those three spots? The star still had a clear flux and the problem can't be in the sky count since it didn't affect other stars in the same images.
I would be interested in any insight on this matter.
For now I will just have to go in and use the formulas IRAF uses by hand for those spots which is just a bit annoying.
Francisco Valdes wrote on Feb 05, 2011
I am not aware that this is a known problem. I am not the author but I am the support person. If you want to have this pursued I would need a well defined test case to diagnose. Ideally this is a tar file with the image data and parameter dumps, along with any description of the steps.
I agree that resorting to hand calculation is annoying.
Frank Valdes
I agree that resorting to hand calculation is annoying.
Frank Valdes
Don Schumacher, Jr. wrote on Feb 05, 2011
I have since gone back and redone the photometry on this object. I used the exact same input images and the exact same comparison stars.
However, now I am no longer getting the random zero error...
I have done it several times now and the output results have consistently been free of zero errors and been giving the same values each time.
So I don't know what was happening before, but it seems to be working now.
However, now I am no longer getting the random zero error...
I have done it several times now and the output results have consistently been free of zero errors and been giving the same values each time.
So I don't know what was happening before, but it seems to be working now.
Last post on Feb 05, 2011