Astrometry Tools¶
Warning
The astrometry output from these routines will only be as good as the estimate of the central ra and dec of the shot, the measurement of the PA and the accuracy of the focal plane and IFUcen files. At this stage the results will at best be only accurate to a few arcseconds.
pyhetdex.coordinates.astrometry
provides tools to
add ra, dec columns to catalogues or WCS headers to FITS files.
One of these tools is called add_ra_dec
executable.
Add ra and dec to a catalogue¶
The command should run on command line if your installation of pyhetdex was successful. The usage instructions are:
usage: add_ra_dec [-h] [--fplane FPLANE] [--fout FOUT] [--ftype FTYPE]
[--astrometry ASTROMETRY ASTROMETRY ASTROMETRY | --image IMAGE]
[--ihmps IHMPS [IHMPS ...] | --ihmp-regex IHMP_REGEX]
files [files ...]
Add ra and dec to a detect or daophot ALLSTAR catalogue.
positional arguments:
files List of files to add ra, dec to
optional arguments:
-h, --help show this help message and exit
--fplane FPLANE Focal plane file
--fout FOUT Filename to write to
--ftype FTYPE Type of input catalogue, to add ra and dec to.
Options: line_detect, cont_detect, daophot_allstar
--astrometry ASTROMETRY ASTROMETRY ASTROMETRY
RA DEC and PA of the focal plane center (degrees)
--image IMAGE An image, with a header to grab ra, dec and PA from
(DONT USE THIS)
--ihmps IHMPS [IHMPS ...]
List of IFU slots
--ihmp-regex IHMP_REGEX
Regex with 1 match group corresponding to IFU slot
You must pass some information about the telescope pointing. The --astrometry
option
is the way to do this, with this option you need to pass the ra, dec and PA (all in degrees)
of the observation e.g. for the M3 commissioning run a good choice is:
--astrometry 205.543395821 28.3792133418 257.654951
These numbers are the position of the center of the optical axis, for HETDEX survey observations they’ll be the positions in the schedule file. For other projects you’ll have to compute it from the acquisition camera or the guide probes. To work out where a particular IFU is with respect to this position, a focal fplane file must also be passed along with some information on the IFU slot of the images. To pass this latter information you can either give a list of IFU slots (in the same order of the input files) e.g.:
--ihmps 074 056 023
or pass a regular expression with which to extract the IFU slot from the file name e.g.:
--ihmp-regex 'detect_(.*)_line.dat'
You can pass one or multiple of: line catalogues from detect, continuum catalogues from detect
or ALLSTAR catalogues from DAOPHOT. All files must be of the same type and the type must
be specified with the --ftype
flag. The output can either be a FITS file or a CSV file,
choose the output type by adding either .fits
or .csv
to the end of the output
filename specified with --fout
.
Here are some examples:
add_ra_dec --fplane fplanetmp.txt \
--astrometry 205.543395821 28.3792133418 257.654951 \
--ftype daophot_allstar --fout cat.fits \
--ihmp-regex '061706_(.*).als' 061706_*.als
or specifying the IFU slots manually:
add_ra_dec --fplane fplanetmp.txt \
--astrometry 205.543395821 28.3792133418 257.654951 \
--ftype daophot_allstar --fout cat.csv \
--ihmps 095 075 073 -- 061706_095.als 061706_075.als 061706_073.als
Note the double-dash --
can be used to explicitly separate the arguments passed to the flags from the final input files. Here’s
a final example with a different input file type:
add_ra_dec --fplane fplanetmp.txt \
--astrometry 205.543395821 28.3792133418 257.654951 --ftype line_detect \
--fout cat.fits --ihmp-regex 'detect_(.*)_.*_line.dat' \
detect_084_20160512T055309.7_line.dat detect_074_20160512T055309.7_line.dat
Convert between x, y on IFU to ra, dec on command line¶
The command line tool xy_to_ra_dec
accepts astrometry info (using the --astrometry
option in the same way as
in add_ra_dec
), reads in a position - with respect to the center of the IFU - and prints
the ra, dec to standard output. Note positions from ds9 or daophot might be with respect the the bottom
left of the IFU, not necessarily the center of the IFU or its position as defined in the fplane file.
Here is the help info:
usage: xy_to_ra_dec [-h] [--fplane FPLANE]
[--astrometry ASTROMETRY ASTROMETRY ASTROMETRY | --image IMAGE]
[--ihmp IHMP]
pos pos
Convert between in-IFU x, y and on-sky ra, dec.
positional arguments:
pos Position in IFU (w.r.t. to IFU position in fplane
file, i.e. the IFU center)
optional arguments:
-h, --help show this help message and exit
--fplane FPLANE Focal plane file
--astrometry ASTROMETRY ASTROMETRY ASTROMETRY
RA DEC and PA of the focal plane center (degrees)
--image IMAGE An image, with a header to grab ra, dec and PA from
(DONT USE THIS)
--ihmp IHMP IFU slot of desired IFU
Here is an example:
xy_to_ra_dec --fplane fplane.txt --astrometry 205.547 28.376 254.6 --ihmp 073 20.969 -23.712
Add in IFU x, y to a catalogue¶
The command line call add_ifu_xy
will add in IFU x,y coordinates (assuming the IFU center is at 0,0) to a catalogue. The columns
of the output file called xifu
, yifu
and ifuslot
store the x and y positions in the IFU specified by ifuslot
.
Allowed input/output catalogue types include .csv files and .fits files. This code associates anything with +/- 30 arcseconds
of an IFU to that IFU. If an object center is in multiple IFUs it only outputs it for one of them, but this can’t occur in
HETDEX unless the dither size becomes comparable to the distance between IFUs. Objects not in an IFU are given the dummy IFU
slot 999, as well as an x, y positions with the dummy value 999.0. Here is the full help info:
usage: add_ifu_xy [-h]
[--astrometry ASTROMETRY ASTROMETRY ASTROMETRY | --image IMAGE]
[--ra-name RA_NAME] [--dec-name DEC_NAME] [--fplane FPLANE]
file fout
Convert between ra, dec to IFU x, y. Note that currently anything within +/-
30 arcseconds of the IFU is output. If IFUs overlap the detection will only be
output for one of them
positional arguments:
file A csv or fits file with ra and dec columns
fout A csv or fits file to output to (including extension:
.fits or .csv)
optional arguments:
-h, --help show this help message and exit
--astrometry ASTROMETRY ASTROMETRY ASTROMETRY
RA DEC and PA of the focal plane center (degrees)
--image IMAGE An image, with a header to grab ra, dec and PA from
(DONT USE THIS)
--ra-name RA_NAME The label of the ra column in the input
--dec-name DEC_NAME The label of the dec column in the input
--fplane FPLANE Focal plane file
Using the --ra-name
and --dec-name
flags you can specify the names of the columns containing ra, dec. The default input column names are
ra
and dec
. For comma-separated files (csv) the column names are read from the first line like this (note no comment character like ‘#’ is expected):
ID,mag,mag_std,sky,niter,CHI,SHARP,ra,dec,ifuslot,xfplane,yfplane
1,17.591,0.051,57.577,4.0,0.52,-0.008,205.52507279787594,28.411966761669696,074,35.458,126.543
Here is an example call:
add_ifu_xy --astrometry 167.0 45.0 89.0 --fplane fplane.txt input.csv output.csv
Add WCS to a fits image¶
Warning
For some reason the x and y coordinates are a flipped in the WCS. So this doesn’t actually work yet…
The routine add_wcs
adds a (2D) WCS header to fits images and datacubes from
VIRUS. The usage is:
usage: add_wcs [-h] [--fplane FPLANE] [--fout FOUT | --pre PRE]
[--imscale IMSCALE]
[--astrometry ASTROMETRY ASTROMETRY ASTROMETRY | --image IMAGE]
file ihmp
Add WCS header to a fits file.
positional arguments:
file Fits file to add WCS to
ihmp The IFU slot of the image
optional arguments:
-h, --help show this help message and exit
--fplane FPLANE Focal plane file
--fout FOUT Name of output file
--pre PRE Prefix to append to output
--imscale IMSCALE Number of arcseconds per pixel
--astrometry ASTROMETRY ASTROMETRY ASTROMETRY
RA DEC and PA of the focal plane center (degrees)
--image IMAGE An image, with a header to grab ra, dec and PA from
(DONT USE THIS)
The --fplane
and --astrometry
parameters are explained above. The inserted
fits header assumes position 24.5 arcsecs, 24.5 arcsecs is the center of your image. It also
assumes no transformations or rotations have been applied to the raw data. Here is an
example:
add_wcs --fplane fplanetmp.txt --astrometry 205.543395821 28.3792133418 257.654951 CuFepses20160604T063029.1_085_sci.fits 085