iraf.net

I've been using psfmeasure for a while now and occasionally get the message "Warning: Invalid Flux Profile". Normally I'll get the message when I'm using a set coordinate file for and entire night and the occasional star drifts of the frame. It makes perfect sense to me that there is an invalid flux profile because there is no flux being recorded from that star and in these cases it isn't a big deal and I ignore the warning. But, I also get the very rare "Warning: Invalid Flux Profiles" for stars that are nowhere near the edge of the frame and "look" to be perfectly fine. I got curious as to what the qualifications are for an "Invalid Flux Profile", but can't seem to find out what causes the error. It didn't seem to be mentioned in the psfmeasure help file and I didn't see it mentioned anywhere on the forums either. Could anyone tell me what causes the error?Thanks.-Craig

Frank may comment in more detail, but in case it elps, that particular message is printed when the computed magnitude is <= 0-Mike

Maybe I can get the extended explanation from Frank...We're using psfmeasure to calculate the psf for a series of stars. We use a set coordinate file for the entire night. During the course of the night, one of the stars drifts off the frame and our script breaks when it tries to run psfmeasure. All we get is the "Warning: Invalid Flux Profile". We have psfmeasure set to write it's output to a text file, but whenever we get the "Warning: Invalid Flux Profile" psfmeasure doesn't write it's output. We want to force it to write the output even if it comes across an error (we don't care what it writes, just that it does it so the script doesn't stop running). Then we can check the contents of the output file and if it was an error deal with it accordingly. Is there any way to do this?Thanks.-Craig

Hi,The PSF fitting is not as robust as I'd like and I wish I had time to work more on it. So I am aware that it sometimes fails to make a good measurement. This happens mostly with "moffat" profiles and the "gaussian" fitting is pretty robust.As to you script question, there isn't any way short of a code change to force some indication that a fit to a star was attempted. However, my suggestion is that you print a dummy line before and the calls to PSFMEASURE. Then if you see these two lines with nothing in-between then you know the fit failed.Sorry for the problem,
Frank Valdes

That's not really the answer that I was hoping for, but it's unfortunately the answer I kind of expected. Oh well, I had already thought about putting dummy lines in, but was hoping to avoid it for sake of the amount of time it adds to the script. It isn't the end of the world, though. Thanks again.-Craig