DAOPHOT Question, PSF Task
dustdevil wrote on Dec 01, 2008
Hello all!
I'm currently using the DAOPHOT package in IRAF and am working with a pretty crowded field here and so I reduced the PSFRAD from the default value of 11 to 5. (the FWHM is about 2 pixels). When I ran the PSF task, though, the output psfimage of residuals still has a radius of 11 pixels, even though I include the verify flag on every step of the procedure DAOPHOT to make the psf radius = 5. Even the header of the residual psfimage says the PSFRAD = 5. Is the resulting residual image from PSF 11-pixels in radius by default?
Hope this hasn't been too cryptic!
Thanks in advance,
dustdevil
I'm currently using the DAOPHOT package in IRAF and am working with a pretty crowded field here and so I reduced the PSFRAD from the default value of 11 to 5. (the FWHM is about 2 pixels). When I ran the PSF task, though, the output psfimage of residuals still has a radius of 11 pixels, even though I include the verify flag on every step of the procedure DAOPHOT to make the psf radius = 5. Even the header of the residual psfimage says the PSFRAD = 5. Is the resulting residual image from PSF 11-pixels in radius by default?
Hope this hasn't been too cryptic!
Thanks in advance,
dustdevil
Francisco Valdes wrote on Dec 01, 2008
This takes a little care in reading the documentation of the PSF format. The residuals are computed on a 2x oversampled grid. Therefore, the size of the image part of the PSF will always be
2 * PSFRAD + 1
So for PSFRAD=5 you get 11 for PSFRAD=10 you would get 21.
Yours,
Frank Valdes
2 * PSFRAD + 1
So for PSFRAD=5 you get 11 for PSFRAD=10 you would get 21.
Yours,
Frank Valdes
Last post on Dec 01, 2008