Formats for IMWCS Match Files

As of version 2.8.7, 10 January 2001, imwcs can use a file of x,y,RA,Dec matches to initialize the WCS fit. If no other catalog is given, the program stops after fitting a WCS to these stars, writing it to the image header, if requested with the -w option. If another catalog is given, imwcs proceeds, as shown in this example. For now, only simple ASCII files are supported. Lines beginning with a # are skipped by imwcs. Only the first four elements of each line are read; x and y may preceed or follow right ascension and declination, though if RA and Dec are first they must be in the colon-separated format. Tabs or spaces may separate the columns. The following files are all legal:

X and Y first, followed by RA and Dec as hh mm ss.sss dd mm ss.ss

72.04   143.88  00 47 10.984    -11 53 18.92
114.91  185.80  00 47 09.153    -11 52 52.70
370.15  400.11  00 46 58.055    -11 50 36.60
325.49  191.93  00 47 00.064    -11 52 49.89
418.23   30.94  00 46 56.044    -11 54 32.13

RA and Dec first as hh:mm:ss.sss dd:mm:ss.ss, followed by X and Y in the TDC ASCII catalog format. /j/n/m indicates to scat, imcat, and any other WCSTools catalog-reading programs that the coordinates are J2000, that no source number preceeds the coordinates, and that no magnitude is present.
```
#ngc246match/j/n/m
#NGC 246 image star coordinates
00:47:10.984 -11:53:18.92 72.04 143.88
00:47:09.153 -11:52:52.70 114.91 185.80
00:46:58.055 -11:50:36.60 370.15 400.11
00:47:00.064 -11:52:49.89 325.49 191.93
00:46:56.044 -11:54:32.13 418.23 30.94
```

X and Y first, followed by RA and Dec as hh:mm:ss.sss dd:mm:ss.ss

72.04   143.88  00:47:10.984    -11:53:18.92
114.91  185.80  00:47:09.153    -11:52:52.70
370.15  400.11  00:46:58.055    -11:50:36.60
325.49  191.93  00:47:00.064    -11:52:49.89
418.23   30.94  00:46:56.044    -11:54:32.13