NAME¶

funsky - convert between image and sky coordinates

SYNOPSIS¶

funsky iname[ext]               # RA,Dec (deg) or image pix from stdin
funsky iname[ext] [lname]       # RA, Dec (deg) or image pix from list
funsky iname[ext] [col1] [col2]         # named cols:units from stdin
funsky iname[ext] [lname] [col1] [col2] # named cols:units from list

OPTIONS¶

  -d        # always use integer tlmin conversion (as ds9 does)
  -r        # convert x,y to RA,Dec (default: convert RA,Dec to x,y)
  -o        # include offset from the nominal target position (in arcsec)
  -v        # display input values also (default: display output only)
  -T        # output display in rdb format (w/header,tab delimiters)

DESCRIPTION¶

Funsky converts input sky coordinates (RA, Dec) to image coordinates (or vice versa) using the WCS information contained in the specified FITS file. Several calling sequences are supported in order to make it easy to specify coordinate positions in different ways.

The first required argument is always the input FITS file (or extension) containing the WCS information in an extension header. Note that the data from this file is not used. By default, the program converts input RA and Dec values to X and Y using this WCS information. If the WCS is associated with a FITS image, then the X,Y values are image values. If the WCS is associated with a binary table, then the X, Y values are physical values. To convert X,Y to RA and Dec, use the -r (reverse) switch.

If no other command arguments are supplied, then the input positions are read from the standard input. Each line is assumed to contain a single coordinate position consisting of an RA in degrees (or X in pixels) followed by a Dec in degrees (or Y in pixels). The usual delimiters are supported (spaces, commas, tabs). For example:

 # read from stdin, default column names and units
 [sh] funsky snr.ev
 22.982695    58.606523   # input RA (hrs), Dec(deg)
    510.00       510.00
 22.982127    58.607634   # input
    512.00       510.50
 22.981700    58.614301   # input
    513.50       513.50
 ^D                       # end of input

If a second argument is supplied, this argument is assumed to be a file containing RA (X) and Dec (Y) positions. The file can either be an ASCII table or a FITS binary table. The order of columns is unimportant, if the table has a column header. In this case, the names of the columns must be one of "RA", "DEC", or "X", "Y" for sky to image and image to sky conversions, respectively. If the table has no header, then once again, RA (X) is assumed to first, followed by DEC (Y). For example:

  # read from file, default column names and units
  [sh] cat hd.in
         RA          DEC
  ---------    ---------
  22.982695    58.606523
  22.982127    58.607634
  22.981700    58.614301

  [sh] funsky snr.ev hd.in
        510.00       510.00
        512.00       510.50
        513.50       513.50

If three arguments are supplied, then the input positions again are read from the standard input. Each line is assumed to contain a single coordinate position consisting of an RA (or X in pixels) followed by a Dec (or Y in pixels), with the usual delimiters supported. However, the second and third arguments now specify the column names and/or sky units using a colon-delimited syntax:

  [colname]:[h⎪d⎪r]

If the colname is omitted, the names default to "RA", "DEC", "X", "Y", "COL1", or "COL2" as above. If the units are omitted, the default is degrees for both RA and Dec. When the -r switch is used (convert from image to sky) the units are applied to the output instead of the input. The following examples will serve to illustrate the options:

  # read from stdin, specifying column names (def. units: degrees)
  [sh] cat hd.in
       MYRA        MYDEC
  ---------    ---------
  22.982695    58.606523
  22.982127    58.607634
  22.981700    58.614301

  [sh] funsky snr.ev MYRA MYDEC < hd.in
        510.00       510.00
        512.00       510.50
        513.50       513.50

  # read from stdin, specifying column names and units
  [sh] cat dd.in
       MYRA        MYDEC
  ---------    ---------
  344.740432    58.606523
  344.731900    58.607634
  344.725500    58.614301

  [sh] funsky snr.ev MYRA:d MYDEC:d < dd.in
        510.00       510.00
        512.00       510.50
        513.50       513.50

  # read stdin, convert image to sky, specifying output sky units
  [sh] cat im.in
        510.00       510.00
        512.00       510.50
        513.50       513.50

  [sh] cat im.in ⎪ funsky -r snr.ev :d :d
  344.740432    58.606523
  344.731900    58.607634
  344.725500    58.614301

Finally, four command arguments specify both and input file and column names and/or units:

  [sh] cat dd.in
       MYRA        MYDEC
  ---------    ---------
  344.740432    58.606523
  344.731900    58.607634
  344.725500    58.614301

  [sh] funsky snr.ev dd.in MYRA:d MYDEC:d
        510.00       510.00
        512.00       510.50
        513.50       513.50

  # read file, convert image to sky, specifying output sky units
  [sh] cat im.in
        510.00       510.00
        512.00       510.50
        513.50       513.50

  [sh] funsky -r snr.ev im.in :d :d
    344.740432    58.606523
    344.731900    58.607634
    344.725500    58.614301

By default, the output of funsky consists only of the converted coordinate position(s), one per output line. This makes parsing in shell scripts easy. Use the -v (verbose) switch to specify that the input coordinates should be pre-pended to each line. For example:

  [sh] cat dd.in
       MYRA        MYDEC
  ---------    ---------
  344.740432    58.606523
  344.731900    58.607634
  344.725500    58.614301

  [sh] funsky snr.ev dd.in MYRA:d MYDEC:d
        510.00       510.00
        512.00       510.50
        513.50       513.50

  [sh] funsky -v snr.ev dd.in MYRA:d MYDEC:d
    344.740432    58.606523       510.00       510.00
    344.731900    58.607634       512.00       510.50
    344.725500    58.614301       513.50       513.50

In addition, a full starbase table can be output using the -T (table) switch. This switch can be used with or without the -v switch. If the -T and -v are both specified, then a descriptive header parameters are output before the table (mainly to remind you of the sky units):

  # output table in non-verbose mode
  [sh] funsky -T snr.ev dd.in MYRA:d MYDEC:d
             X               Y
  ------------    ------------
        510.00          510.00
        512.00          510.50
        513.50          513.50

  # output table in verbose mode
  [sh] funsky -T -v snr.ev dd.in MYRA:d MYDEC:d
  # IFILE = /Users/eric/data/snr.ev
  # ICOL1 = MYRA
  # ICOL2 = MYDEC
  # IUNITS1 = d
  # IUNITS2 = d
  # OCOL1 = X
  # OCOL2 = Y

          MYRA           MYDEC               X               Y
  ------------    ------------    ------------    ------------
    344.740432       58.606523          510.00          510.00
    344.731900       58.607634          512.00          510.50
    344.725500       58.614301          513.50          513.50

Finally, the -d (ds9) switch mimicks ds9's use of integer TLMIN and TLMAX values for all coordinate transformations. FITS conventions seem to call for use of floating point TLMIN and TLMAX when the data are floats. This convention is followed by funsky but results in a small discrepancy with ds9's converted values for floating point data. We will remedy this conflict in the future, maybe.

SEE ALSO¶

See funtools(7) for a list of Funtools help pages