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Name

wcs - World Coordinate Systems

Synopsis

wcs [parameter=value]

Description

wcs is the World Coordinate System.

Polarization

Polarization is an exceptional case, since it’s enumerated (XX, YY, LL, etc.), but the community has assigned integer values such that a usual NAXIS,CRPIX,CRVAL,CDELT,CTYPE can be used. This is the AIPS/FITS convention. 
1    I    Standard Stoked Unpolarized
2    Q
3    U
4    V
-1    RR    Right-right circular
-2    LL
-3    RL
-4    LR
-5    XX    X parallel linear
-6    YY
-7    XY
-8    YX

Coordinates

Some common coordinate systems: 
   RA--    Equatorial
   DEC-
   GLON    Galactic
   GLAT
   ELON    Ecliptic
   ELAT

Projection

Some common projections: 
   -SIN
   -TAN
   -ARC
   -NCP
   -GLS (or -SFL)
   -MER
   -AIT

Velocity Convenctions

Radio vs. Optical. Linear vs. Non-linear. See also ccd2vel(1NEMO) 

  FREQ
  WAVE (vacuum)
  AWAV (air)
  VRAD (radio)
  VOPT (optical)
  VELO (relativistic)
  FELO [VOPT-F2W)
  -HEL
  -LSR

Issues

Why is it so hard to make a non-sky coordinates rectilinear system that programs like ds9 (and carta?) understand?

See Also

wcs(1NEMO) , worldpos(3NEMO) , ccdsky(1NEMO) , ccdfits(1NEMO) , impos(1MIRIAD) , xy2sky(1WCSTOOLS) , sky2xy(1WCSTOOLS)

https://www.aanda.org/articles/aa/pdf/2006/05/aa3818-05.pdf - Representations of spectral coordinates in FITS

Author

Peter Teuben

Update History


15-dec-2019    written        PJT

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