DAOPHOT-type Photometry March 2008 These are a set of IDL procedures adapted from an early FORTRAN version of DAOPHOT aperture photometry. The creators of DAOPHOT have no responsibility whatsoever for the IDL code. The IDL code will give similar, but not identical, results as the original FORTRAN. A LaTex file daophot.tex in /text supplies further documentation for the IDL-DAOPHOT procedures for CCD images. The PSF fitting portion of the code (e.g. nstar.pro) is now fairly obsolete, but the routines for source detection, aperture photometry and sky level determination have been kept up to date. Changes: March 2008: GCNTRD - Modified to match IRAF/DAOFIND and use a more accurate (though possibly less robust) FIND - Now uses the Gaussian fits to the marginal X & Y distributions (as in GCNTRD) rather than finding where the derivative goes to zero. June 2004: SKY,MMM updated to better match more recent versions of DAOPHOT June 2004: the procedure GCNTRD was added to determine centroids using Gaussian fits to the marginal X and Y distributions. This is similar to the method used in current DAOPHOT versions, and allows the user to ignore possible bad pixels. (Very early -- pre-1987 -- versions of DAOPHOT used the centroid algorithm in CNTRD.PRO where the centroid is located where the X and Y derivatives go to zero.) June 2000: the procedure aper.pro was modified to allow it to compute the exact area of the intersection of a circle with square pixels. July 1997: the procedures were modified so that the PSF residuals are written to a FITS file, rather than a STSDAS file. To convert a PSF file 'psfname' created earlier in STSDAS format, use the following commands: IDL> sxopen,1,'psfname',h IDL> psf = sxread(1) IDL> writefits,'psfname.fits',psf,h May 1996: the following updates were made to the code (1) Non-standard system variables are no longer used. The PRINT keyword is used instead of !TEXTOUT, and the DEBUG keyword is used instead of !DEBUG. (2) The T_* procedures now request the *name* of a disk FITS ASCII table for storing the input and output results. (3) NSTAR now has a /VARSKY keyword to allow the skylevel to vary.