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Institut für Astronomie und Astrophysik

Abteilung Astronomie

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Table of Contents



Introduction

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 slight modification of the procedures for use with digitized photographs is available from the UIT (Ultraviolet Imaging Telescope) group. A LaTex file DAOPHOT.TEX in /text supplies further documentation for the IDL-DAOPHOT procedures for CCD images.

Before March 1995, the FITS table procedures in this directory would write TTYPE* values with embedded spaces. This practice is strongly discouraged within the FITS community, and has now been changed (e.g. "STAR_ID" is written instead of "STAR ID"). A procedure FIXDAOTAB is available from Wayne Landsman to correct FITS tables created before March 1995.

In 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.
In 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


Index of Subroutines

APER Compute concentric aperture photometry (adapted from DAOPHOT)
CNTRD Compute the centroid of a star using a derivative search
DAO_VALUE Returns the value of a DAOPHOT point-spread function at a set of points.
DAOERF Calulates the intensity, and derivatives, of a 2-d Gaussian PSF
FIND Find positive brightness perturbations (i.e stars) in an image
GCNTRD Compute the stellar centroid by Gaussian fits to marginal X,Y, sums
GETPSF To generate a point-spread function (PSF) from observed stars.
GROUP Assign stars with non-overlapping PSF profiles into distinct groups
MMM Estimate the sky background in a stellar contaminated field.
NSTAR Simultaneous point spread function fitting (adapted from DAOPHOT)
PIXWT Circle-rectangle overlap area computation.
PKFIT Subroutine of GETPSF to perform a one-star least-squares fit
RDPSF Read the FITS file created by GETPSF in the DAOPHOT sequence
SKY Determine the sky level in an image using the the procedure MMM
SRCOR Correlate the source positions found on two lists.
SUBSTAR Subtract a scaled point spread function at specified star position(s).
T_APER Driver procedure (for APER) to compute concentric aperture photometry.
T_FIND Driver procedure (for FIND) to locate stars in an image.
T_GETPSF Driver procedure (for GETPSF) to generate a PSF from isolate stars.
T_GROUP Driver procedure (for GROUP) to place stars in non-overlapping groups.
T_NSTAR Driver procedure (for NSTAR) for simultaneous PSF fitting.
T_SUBSTAR Driver procedure (for SUBSTAR) to subtract scaled PSF values
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Jörn Wilms (wilms@astro.uni-tuebingen.de)
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