ahedit: Initialize the image wcs and set standard keywords

Package: astcat

Usage

ahedit images imsurveys

Parameters

images

The list of input images to be edited.

imsurveys

The input image survey that is the source of the input images. If imsurveys is defined then the wcs status and the wcs and standard keyword parameter names and values are read from the image survey configuration file imdb. If imsurveys is undefined these quantities are read from the wcs parameter and the default awcspars and aimpars parameter sets.

hupdate = yes

Update the image headers ? If hupdate = no the image header edits are listed but the headers are not updated.

wcsedit = no

Convert a DSS WCS to a FITS WCS or add an approximate FITS style WCS to the input image headers ? If imsurveys is defined the WCS status of the survey images plus approximate image center coordinates, scale, orientation, and projection information are read from the image surveys configuration file imdb. If imsurveys is undefined these quantities are read from the wcs parameter and awcspars parameter set.

wcs = "none"

The default wcs status of the input images if imsurveys is undefined. The options are:

fits

The input image is assumed to have a FITS WCS. No new FITS WCS is written.

dss

The input image is assumed to have a DSS WCS. The equivalent FITS WCS is added, but the DSS WCS is left unchanged.

none

The input image is assumed to have no WCS. The parameters in awcspars are used to create an approximate FITS WCS.

awcspars = ""

The default WCS parameter set. If wcsedit = yes and imsurveys is undefined then the awcspars parameters are used to create an approximate FITS WCS. For more information about the awcspars parameters type "help awcspars".

hdredit = no

Add a set of standard keywords to the image header which may be required or useful in the later astrometric analysis steps ? These parameters divide into two groups, those concerned with locating objects in an image and those required to transform from mean place to observed coordinates. If imsurveys is undefined the standard keyword names and values are read from the images surveys configuration file imdb. If imsurveys is defined they are read from the aimpars parameter set.

aimpars = ""

The default standard image header keywords parameter set. If hdredit = yes and imsurveys is undefined the parameter names and values in aimpars are used to write the standard image header keywords. For more information about these parameters type "help aimpars".

update = no

Update the default values of the algorithm parameter sets, e.g. aregpars, awcspars, and aimpars on task termination ?

verbose = yes

Print status messages on the terminal as the task proceeds ?

imdb = "astcat$lib/imdb.dat"

The image surveys configuration file. Imdb defaults to the value of the package parameter imdb. The default image surveys configuration file is "astcat$lib/imdb.dat".

Description

Ahedit adds an approximate FITS WCS and / or a standard set of keyword value pair to the list of images images extracted from the image survey imsurveys. If hupdate = no the image edits are listed but not implemented.

If wcsedit = yes then either an existing DSS WCS is converted to a FITS WCS or an approximate FITS WCS is added to the input image. If imsurveys is undefined the current WCS status and WCS information is read from the image surveys configuration file imdb. If imsurveys is undefined the WCS status and coordinate information are read from wcs parameter and the default WCS parameter set awcspars. In both cases the quantities of interest are the values, units, and coordinates system of the reference point wxref, wyref, wraref, wdecref, wraunits, wdecunits, and wsystem, and the image scale, orientation, and projection information wxmag, wymag, wxrot, wyrot, and wproj. For more information on how these quantities are defined in the image surveys configuration file or the awcspars parameter set type "help imsurveys" and / or "help awcspars".

If hdredit = yes then a standard set of keyword equal value pairs are added to the image headers. If imsurveys is defined the standard keyword name and value pairs are read from the image surveys configuration file. If imsurveys is undefined they are read from the standard image keywords parameter set aimpars. In both cases the parameters divide into two groups, those concerned with locating stars in the image and computing accurate pixel centers edatamin, edatamax, egain, and erdnoise, and those required for transforming mean place coordinates to observed plate coordinates, observat, esitelng, esitelat, esitealt, esitetz, emjdobs, ewavlen, etemp, and epress. New keyword values are only added to the header if keywords of the same name do not already exist, and if appropriate values for the keywords exists, i.e. "INDEF" valued parameters will not be added to the header.

If update = yes then the fIawcspars, and aimpars parameter sets are updated at task termination. If verbose = yes then detailed status reports are issued as the task executes.

Examples

1. List the header edits required to create a FITS WCS from a DSS WCS for a set of images extracted from the dss1@cadc.

cl> ahedit @imlist dss1@cadc hupdate- wcsedit+ hdredit-

2. Repeat the previous example but actually do the edits.

cl> ahedit @imlist dss2@cadc hupdate+ wcsedit+ hdredit-

3. Repeat the previous example but get the current WCS stats from the user rather than from the image survey configuration file.

cl> ahedit @imlist "" hupdate+ wcsedit+ wcs=dss hdredit-

4. Add an approximate FITS WCS to an image for which the coordinates of the image center in hours and degrees are stored in the keywords RA and DEC, the epoch of the image center coordinates is stored in EQUINOX, the image scale is 0.261 arcsec per pixel and east is left and north is down.

cl> ahedit image "" wcsedit+ wcs="none" wraref="RA" wdecref="DEC" \
wxmag=0.26 wymag=0.26 wxrot=270 wyrot=90 wsystem="EQUINOX" hdredit-

5. Add the standard keyword name and values pairs for a list of images extracted from the dss1@cadc.

cl> ahedit @imlist dss1@cadc hupdate+ wcsedit- hdredit+

6. Store the CCD saturation limit in the image header in the EDATAMAX keyword. Set the minimum good data limit at the same time.

cl> ahedit image "" hupdate+ wcsedit- hdredit+ edatamin=-100.0 \
edatamax=32000

Time requirements

Bugs

See also

aslist, adumpim, aregpars, awcspars, aimpars