| skypix | xray.xspatial | skypix |
skypix -- convert and precess astronomical coordinate systems
skypix isystem osystem ifile
Skypix transforms a list of coordinates from one coordinate system to another. The EQUATORIAL keyword is optional as the actual system is specified by the type of epoch. For Julian epochs FK5 is assumed and for Besselain epochs FK4.
Input/Output coordinate systems. Specified with the following syntax:
<imagefile> -- Image pixels. [Equatorial] Jxxxx.xx -- FK5 system with Julian equinox. [Equatorial] Bxxxx.xx[@xxxx.xx] -- FK4 system with Besselian equinox and optional Bessalian observation epoch. Ecliptic xxxx -- Ecliptic system with equinox Galactic -- Galactic system SuperGalactic -- SuperGalactic system Image -- Pseudo system. If one of the coordinate systems (input or output) is a reference image the other may be specified as Image. The sky system of the image will be used for this system. This can be used to convert between world and physical coordinates, e.g. degrees -> pixels or pixels -> degrees
Comma separated list of the input files to be read. STDIN is allowed (Remember to use ^D end of file for STDIN).
Name of the output file to be created.
The units of the output coordinate list (degrees, hours, radians). If the coordinate system is specified to be a reference image the units are taken to be pixels.
Boolean flag specifying whether or not the output coordinate list file can be overwritten, if it already exists.
Display level print out flag.
0 -- print only the converted coordinates 1 -- print parsed conversion specification to STDERR 2 -- print both input and converted coordinates in output file and short informative header to output (but not STDOUT). 3 -- show coordinate conversions as they are done. 4 -- show units conversions.
Input string + formatting spec.
Output string + formatting spec.
Examples of coordinate system specification.
xdata$snr.qp # xdata$snr.qp pixels EQUATORIAL J2000 # FK5 equinox 2000 J2010.9 # FK5 equinox 2010.9 B1950 # FK4 equinox 1950Execution Examples:
1. Transform a source position in the xdata$snr.qp file to J2000 coordinates ( xdata$snr.qp is in B1950 coordinates, observed in 1980 ) The RA and Dec ("22:08:41.56 45:44:49.6") were typed in as standard input (STDIN). Typing "^D" ended the standard input.
xs> skypix
input cooordinate system (xdata$snr.qp):
output cooordinate system (J2000):
input file list (STDIN):
Converting from xdata$snr.qp is
TANGENT 512. 513. -0.002222222 0.002222222 =
22:58:55.66 58:36:47.5 0.
EQUATORIAL B1950. in pixels
to EQUATORIAL J2000. in hours
(Terminate interactive list with <cntl>-D)
22:08:41.56 45:44:49.6
23:09:12.7 57:49:47.6
<cntl-d>
xs>
2. Transform the list of Eoscat sources from their FK5 J2000
positions to their FK4 B1950 positions. The input file has the
positions listed in radians. The output will be sent to STDOUT and
will be formatted in hours minutes seconds, degrees minutes seconds
units.
cl>skypix iformat=rad oformat=hours
input coordinate system : J2000
output coordinate system : B1950
input file list (STDIN): /Eoscat/2000R
Converting from EQUATORIAL J2000.00 in radians
to EQUATORIAL B1950.00 in hours
0:00:36.00 21:41:59.93
0:02:18.00 -42:12:59.76
0:02:24.00 -30:50:59.62
0:03:12.00 72:29:59.59
...
3. Transform the galactic coordinate to RA and Dec
showing the steps used to complete the transformation. Here the
input coordinate is read from STDIN and the output typed to
STDOUT. The value of display causes the steps to be printed and
the input coordinates to be echoed. The pixels are referenced from
the world coordinate system of the image xdata$snr.qp
xs> skypix iformat=degrees display=4
input cooordinate system (galactic):
output cooordinate system (xdata$snr.qp):
input file list (STDIN):
Converting from GALACTIC in degrees
to xdata$snr.qp is
TANGENT 512. 513. -0.002222222 0.002222222 =
22:58:55.66 58:36:47.5 0.
EQUATORIAL B1950. in pixels
(Terminate interactive list with <cntl>-D)
109.1 -.99
Convert Galactic to B1950FK4
Convert sky coordinates to image pixels
109.1 -0.99 500.7361 516.321
<cntl-d>
xs> wcscoords
IRAF reference image (xdata$rp110590.qp[bl=30]): xdata$snr.qp
Menu for coordinate conversion
1 = world -> physical
2 = world -> tv
3 = world -> logical
4 = physical-> logical
5 = physical-> world
6 = physical-> tv
7 = tv -> physical
8 = tv -> world
9 = tv -> logical
10= logical -> physical
11= logical -> world
12= logical -> tv
code for conversion type (0:12) (12): 5
input coordinate list (STDIN):
Converting from xdata$snr.qp is
TANGENT 512. 513. -0.002222222 0.002222222 =
22:58:55.66 58:36:47.5 0.
EQUATORIAL B1950. in pixels
to xdata$snr.qp is
TANGENT 512. 513. -0.002222222 0.002222222 =
22:58:55.66 58:36:47.5 0.
EQUATORIAL B1950. in hours
(Terminate interactive list with <cntl>-D)
500.7361 516.321
Convert image pixels to sky coordinates
500.7361 516.321 22:59:07.2 58:37:14.0
<cntl-d>
xs>
The time requirements for this tasks are negligible.
Documentation on precess (help precess ) for a description of the precess task.
Documentation on IRAF WCS coordinate conversions (help wcscoords ) for a decription of the coordinate conversions within IRAF.
See also help rimcursor ,
help tvlabel , and
help xexamine and help
MWCS help file (mwcs$MWCS.hlp fi+ ) for a description of the Mini-WCS (World Coordinate System) Interface.