funsky - Online in the Cloud

PROGRAM:

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.

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