lickast.cl

NAME

lickast -- Add IMAGETYPE to Lick images, and other astrometric keywords

USAGE

lickast input catalog [observat]

PARAMETERS

input: Images whose headers will be made astrometrically accurate.
catalog: A data file giving astrometrically precise positions of the objects which were observed in the input images.
observat: Optional parameter which permits setting of the IRAF observatory ID. This will be inserted if it is not a null string and if the header does not already contain an OBSERVAT card.

DESCRIPTION

This task rewrites image headers to insert astrometrically accurate values of telescope pointing keywords and other positional information. The task also inserts IRAF "imagetyp" cards so as to assist with further processing by the tasks in noao.imred.ccdred ccdproc. The user provides a catalog containing accurate positions for all objects.

Users of the Lick telescopes are aware that the RA, DEC, and HA cards are not as accurate as the observer might like. There is hysteresis and other nonlinear effects in the telescope pointing encoders which lead to discrepancies between reality and the values which TELCO inserts into the FITS headers. There are also a number of cards used by various IRAF tasks which are not inserted by the Lick data acquisition system.

This task was originally created to insert an accurate value for the HJD card. Along the way it inserts UT, EPOCH, IMAGETYP, ST, JD, LJD, AIRMASS, and UTMIDDLE. (Note that EPOCH is a misnomer from early FITS usage and should really be EQUINOX.)

To prevent destruction of information the original contents of the RA, DEC, and HA cards are copied into RATELCO, DECTELCO, and HATELCO. If these *TELCO cards already exist, they are not altered.

CATALOG FILE

The catalog file contains one line for each different FITS OBJECT card (or IRAF "title" card) in the list of images being processed. Lines beginning with "#" are ignored, so the file can be liberally sprinkled with comments. Each noncomment line should contain a title, RA, Dec, Equinox, and Imagetype. The title is separated from the rest of a line by the ASCII character "'"; the rest of the entries are separated by white space. RA and Dec should be expressed in hours and degrees respectively, and IRAF sexagesimal notation is permitted. Equinox should denote the precessional date (when the coordinates are valid) expressed in years. Imagetype should be one of the legal IRAF image types as expected by the tasks in noao.imred.ccdred ccdproc (e.g., zero, flat, object, etc.). RA, Dec, and Equinox are allowed to have the special value TELCO if it is desired not to modify the original contents of those cards.

An example catalog file follows:

#########################################################################
# This file is used to associate astrometrically accurate positions     #
# with the names found in the 'title' cards of a bunch of IRAF images.  #
# It is also used to associate an noao.imred.ccdred 'imagetyp' with     #
# each different name found in the 'title' cards.                       #
#                                                                       #
# Steve Allen  1994 September                        #
#                                                                       #
# The commentary information in this data file is                       #
# Copyright (c) 1993,1994 Steven L. Allen                               #
#########################################################################
# Note carefully that the single quote serves as a delimiter between
# the name (which may include spaces and double quotes) and the position.
# The IRAF script mkcattmpl.cl assists in the construction of this file
# by running thru a whole bunch of images and extracting unique OBJECT cards.
# The IRAF script lickast.cl takes this file as input and edits these values
# into the images while still preserving the original TELCO positions.
#
# title         ra              dec             equinox         imagetyp
Dark'           TELCO           TELCO           TELCO           zero
Dome Flat "B"'  TELCO           TELCO           TELCO           flat
Dome Flat "I"'  TELCO           TELCO           TELCO           flat
Dome Flat "R"'  TELCO           TELCO           TELCO           flat
Dome Flat "V"'  TELCO           TELCO           TELCO           flat
# HD8358 = BD-00  210 = SAO 109840 = ACRS 011992 = BI Ceti = GSC 00021 01287
# it is in the SAOJ2000, ACRS, HD, SB8, and HST GSC.
# This position is a hand-obtained mean for the epoch of the observation.
HD8358 "B"'     1:22:50.334     0:42:40.86      2000.           object
HD8358 "I"'     1:22:50.334     0:42:40.86      2000.           object
HD8358 "R"'     1:22:50.334     0:42:40.86      2000.           object
HD8358 "V"'     1:22:50.334     0:42:40.86      2000.           object
# V471 Tauri = BD+16  516A
# it is in the SB8 and PARALLAX catalogs.  Parallax = +0.0138+/-0.0023 arcsec.
# this position from SB8, epoch and equinox B1900
#V471 Tauri'    3:44.5          16:57           1900.           object
# this position from PARALLAX, epoch and equinox B1900
#V471 Tauri'    3:44:33         16:56:47        1900.           object
# this position from PARALLAX after hand-adding proper motion to epoch 1992.8
V471 Tauri'     3:44:41.3       16:56:46.4      1900.           object

BUGS

This task does not use any fancy hashing schemes to store the catalog of objects. Very large catalogs will give slow results.

OBJECT cards in the FITS header (or "title" cards in IRAF) may not contain the character "'".