radial aperture phot with daophot
MichaelCampbell wrote on Jul 15, 2009
Hi,
I am trying to do radial aperture measurements on a cluster which is situated in the bottom corner of my image. I seem to be limited to using radial apertures up to the edge of the image. Is it possible to increase the aperture radii further where part of the selected aperture is off the image? The flux value for the region of the aperture still in the image is useful, and a correction could be made for the part of the aperture off the image.
I have tried this with both the phot package in daophot and apphot, but have not been able to work out how to do it with either. Any help would be much appreciated.
Thanks
Mike
I am trying to do radial aperture measurements on a cluster which is situated in the bottom corner of my image. I seem to be limited to using radial apertures up to the edge of the image. Is it possible to increase the aperture radii further where part of the selected aperture is off the image? The flux value for the region of the aperture still in the image is useful, and a correction could be made for the part of the aperture off the image.
I have tried this with both the phot package in daophot and apphot, but have not been able to work out how to do it with either. Any help would be much appreciated.
Thanks
Mike
Mike Fitzpatrick wrote on Jul 15, 2009
I was hoping somebody with more experience in this would reply, but an idea you might consider is simply copying your image in to a larger blank image so there are enough zero pixels on the border to include your radius. This would allow the radius to extend beyond your data without worrying about boundary problems without contributing any signal to the aperture. The MKPATTERN task in ARTDATA can create a blank image, and you can IMCOPY the image into to blank data using sections. Hope this helps.
-Mike
-Mike
MichaelCampbell wrote on Jul 15, 2009
Hi,
Yeah was considering that, but thought there must be a program that already deals with it. I imagined that it must be a fairly common procedure, so there must be a way of doing it iraf, where the number of pixels, hence the fraction of radii in the image, is also calculated.
Anyway, thanks for the reply. I will do as suggested, then run a monty carlo simulation to calculate the fractional area within the image.
Ta
Mike
Yeah was considering that, but thought there must be a program that already deals with it. I imagined that it must be a fairly common procedure, so there must be a way of doing it iraf, where the number of pixels, hence the fraction of radii in the image, is also calculated.
Anyway, thanks for the reply. I will do as suggested, then run a monty carlo simulation to calculate the fractional area within the image.
Ta
Mike
Last post on Jul 15, 2009