DAOPHOT is a stellar photometry package designed by Peter Stetson at DAO to deal with crowded fields. The package performs various tasks including finding objects, aperture photometry, obtaining the point-spread function, and profile-fitting photometry. Profile fitting in crowded regions is performed iteratively, which improves the accuracy of the photometry.
This document is an introduction to DAOPHOT II: The Next Generation. It replaces the previous
version which is known as DAOPHOT Classic. The main changes concern the choice of the
point-spread fitting function and the handling of under-sampled data. This version uses image data
written in NDF, the Starlink N-Dimensional Data Format (SUN/33), that contain a DATA_ARRAY
component and have an extension .sdf
.
A document written by Peter Stetson (DAOPHOT: A computer program for crowded-field stellar photometry, Publ.astr.Soc.Pacific, 99, 191-222, 1987) gives the background to the algorithms used by DAOPHOT. A user’s manual (MUD/9) is also available through Starlink.
DAOPHOT does not directly use an image display, which is one of the reasons why the package has been successfully ported round the world. Three additional routines have therefore been supplied which allow results obtained with DAOPHOT to be displayed on an image device.
The routine DAOGREY (see §3) will display a grey scale image of the data on a suitable device. DAOPLOT (see §4) will indicate the positions of objects found with DAOPHOT on top of the grey image. DAOCURS (see §5) will put up a cursor on the display to allow positions to be measured from the screen. Although KAPPA (SUN/95) routines could be used for the image display and cursor interaction, DAOPHOT does not comply with the Starlink coordinate system convention (SUN/33) and thus any coordinates would be half a pixel out.
DAOPHOT is copyright of Peter Stetson at the Dominion Astrophysical Observatory. The algorithms should not be changed without permission.