galactic: Convert ra, dec to galactic coordinates

Package: astutil

Usage

galactic files

Parameters

files: The name of a file (or a file list or template) containing the coordinates to be converted.

in_coords = "equatorial": Type of input coordinates. May be either "equatorial" (RA and DEC) or "galactic" (l and b).

print_coords = yes: If print_coords = yes, the RA, DEC and epoch (as well as lII and bII) will be listed on the output file.

Description

Program galactic is used to convert between equatorial and galactic coordinates. It converts in either direction based on the specified input coordinates. Coordinates are read from the input file as RA and DEC or galactic longitude and latitude pairs, one pair per input line. Each coordinate pair may optionally be followed by the epoch of the equatorial coordinates, in which case the coordinates are precessed to 1950.0 (the epoch of definition for the galactic center) before conversion for equatorial to galactic or to the specified epoch for galactic to equatorial. Coordinates may be entered in either decimal or sexagesimal notation.

Examples

1. Convert the given RA and DEC coordinates to galactic coordinates. When the epoch is specified as other than 1950.0, precess before converting. The lines input by the user are marked:

cl> galactic STDIN                              [input]
12:30:10.12 10:18:27.5 1930.                    [input]
12:30:10.12   10:18:27.5  1930.00     288.4695   72.2884
12:30 10:18                                     [input]
12:30:00.00   10:18:00.0  1950.00     287.4598   72.3202
12.5  10:18                                     [input]
12:30:00.00   10:18:00.0  1950.00     287.4598   72.3202
(eof=<ctrl/z>)                                  [input]

2. The following is equivalent, except that coordinate input is taken from the file "coords", rather than from the terminal:

cl> galactic coords                             [input]
12:30:10.12   10:18:27.5  1930.00     288.4695   72.2884
12:30:00.00   10:18:00.0  1950.00     287.4598   72.3202
12:30:00.00   10:18:00.0  1950.00     287.4598   72.3202

3. If image headers contain the coordinates, in this case RA, DEC, and EPOCH, then one can get the galactic coordinates for the image by:

cl> hselect *.imh ra,dec,epoch yes | galactic STDIN

(Consult the help for the task hselect for information about selecting fields from image headers.)