Including WCS information in FITS headers

To incorporate WCS information in fits files generated from the DPOSS plate scans for a particular part of the sky, use:

makeimage.pl

This program needs the following as input:
RA, Dec, size in arcsec, filter, outimage_name, blocks_exist?, clean_blocks?
Any of the three filters can be chosen. If run on DPOSS as user DPOSS one has the choice of pulling pixels from the HPSS (well, once the ATM is restored anyway).
Example use:

makeimage.pl 220.0 33.1 300 f foo.fits y n

make a 300x300 image around RA=220 degree and Dec=33.1 degree using the f plate.
foo.fits is the image created.
The following "y" is to say: "Use existing blocks" .
The last "n" is to say: "Do not clean blocks after use".
WCS information is used from the original plate header.
If the arguments are not given on the command line, the user is prompted for them.

One can also include WCS information in fits files for individual blocks or for an entire plate. One can in fact match USNO A2 stars with catalog positions without having the images on disk and then at a later stage when the fits blocks have been downloaded use the matching to insert the WCS information in the headers.

Here is a breakdown of the steps:
Step 1: Generate fits header for a given block:

match_block.pl xYYY m n


generates wcsheadxYYY_mmnn.fits (5660 bytes). Alternately,

match_plate.pl xYYY


does it to all columns (m=1..23) and all rows (n=1..23).

Step 2: Merge the fits header generated above once you have the corresponding block of image on disk

merge_block_wcs.pl xYYY m n platedir


merges wcsheadxYYY_mmnn.fits with platedir/xYYY/tmmnn.fits and gives wcsxYYY_mmnn.fits with WCS incorporated. platedir is optional and defaults to PWD if not provided.

Here is a recipe to generate DPOSS fits images with WCS for any small region: (lets assume we are interested in the HDF at: 12 36 49.4 +62 12 58)

what_plate 12 36 49.4 +62 12 58 gives:


Plate Number --> 131
Distance from the center --> 2.247

hms_to_dec 12 36 49.4 +62 12 58 gives:


189.205833 62.216111

get_plate_xy_from_rd f131 0 189.205833 62.216111 gives:


13639.26 20130.34

identify_block_from_xy.pl 13639.26 20130.34 gives:


14 20 5.5 11.6 11.2 5.8 (arcmin)
indicating that our target is well centered in block 14 20 of f131.

hpssPullPlate f131
match_block.pl f131 14 20
merge_block_wcs.pl f131 14 20

lands us with wcsf131_1420.fits all ready to go.
This is the alternative to using WCS headers from the plates as in makeimage.pl above.

Status of USNO A2 - DPOSS plate matching.

Last Outdated: 12 Nov 2000