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[color=red:91c753834f]Note: posted on behalf of user by moderator.[/color:91c753834f]I have a problem with daophot. I can't find any answer on the iraf.net forum. If you or somebody can help, I am much appreciated.I am working on images of different filters (same field). It is a very crowded stellar field. I follow the standard daophot handbook instruction: run daofind --> phot --> pstselect (interactively) --> psf --> nstar --> substar. The substar image is used to evaluate the psf model. I delete bad stars from pst file and re-iterate with psf --> nstar --> substar. Once the subtraction is clean, I create the final psf model and run allstar.I have no problem for getting reasonable subtracted images after running substar for two images. However, problem arises on the third image. The psf model looks normal but the subtracted image doesn't look clean. The bright star has been subtracted but the grouped neighboring stars haven't (see eg: attached screenshot). No matter how many bad stars I delete from the pst file, the result remains the same. I suspect something goes wrong during the run of nstar because most of the outputs look like this:Group: 17 contains 4 stars
Star 21 has been deleted because it is too faint
Star 81 has been deleted because it is too faint
Star 37 has been deleted because it is too faint
ID: 50 XCEN: 138.25 YCEN: 16.40 MAG: 18.34
ID: 37 XCEN: 155.07 YCEN: 12.41 MAG: INDEF
ID: 81 XCEN: 134.32 YCEN: 27.19 MAG: INDEF
ID: 21 XCEN: 131.37 YCEN: 7.39 MAG: INDEFI check the magnitude file. Star 21, 37 and 81 have valid magnitude. They are faint in other filters as well. Thus, it doesn't explain to me why it claims to be faint in this filter but not the other. Any idea of why neighboring stars aren't subtracted even though the psf model looks fine? I exercise the same procedures as I did for other two images. I try to change psfrad and fitrad, nothing seems to help.Some important parameters that I use.datapars:
fwhmpsf = typical fwhm of stars in the image
sigma = 0.4--0.6 (rather low but that's what the imexam "m" tells me)findpars:
threshold = 4--4.5centerpars:
calgori=nonefitskypars:
salgori=mode
annulus= 4*fwhm
dannulus= 4*fwhmphotpars:
aperture: fwhmdaopars:
function= auto
varorder = 1 or 2
psfrad = 4*fwhm + 1
fitrad = fwhm
recenter=yes
fitsky=no
groupsk=yes
maxiter=15 (raised to 15 after suspecting it fails to fit neighboring stars)the rests are default.Thanks![img:91c753834f]http://iraf.noao.edu/irafnet_images/BiQing.jpg[/img:91c753834f]