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Basic Information on fits


Task: fits
Purpose: Conversion between Miriad and FITS image and uv formats
Categories: data transfer

        FITS is a Miriad task that converts image and uv files both
        from FITS to Miriad format, and from Miriad to FITS format.
        Note that because there is not a perfect correspondence between
        all information in a FITS and Miriad file, some information may
        be lost in the conversion step.  This is particularly true for
        uv files.
 
 
        WARNING: When writing uv FITS files, fits can handle single
        frequency band, single array configuration only. Minimal
        checks are made to see that these restrictions are observed!
 
        References:
          For a description of the standard, see
            http://fits.gsfc.nasa.gov/fits_home.html
 

Key: in
        Name of the input file (either a FITS or Miriad file name,
        depending on OP).  No default.

Key: op
        This determines the operation to perform. Possible values are:
          "uvin"    Convert FITS uv file to Miriad uv file.
          "uvout"   Convert Miriad uv file to FITS uv file.
          "xyin"    Convert FITS image file to Miriad image file.
          "xyout"   Convert Miriad image file to FITS image file.
          "print"   Print out a FITS header.
        There is no default.

Key: out
        Name of the output file (either a Miriad or FITS file name,
        depending on OP).  If op=print, then this parameter is not
        required.  Otherwise there is no default.

Key: line
        Line type of the output, when op=uvout. This is of the form:
 
          linetype,nchan,start,width,step
 
        "Linetype" is either "channel", "wide" or "velocity".  "Nchan"
        is the number of channels in the output.

Key: region
        The region of interest. The default is the entire input image.
        See the Users Manual for instructions on how to specify this.
        Used when op=xyout

Key: select
        Normal uv selection, used when op=uvout.

Key: stokes
        Normal Stokes selection, used when op=uvout

Key: options
        These options applies for op=uvin only.
          compress Store the data in compressed uv format.
          nochi    Assume that the parallactic angle of the
                   telescope is a constant 0 (or that the data are
                   from circularly polarised feeds and have already
                   been corrected for parallactic angle).
          lefty    Assume that the FITS antenna table uses a
                   left-handed coordinate system (rather than the
                   more normal right-handed system).
          varwt    The visibility weight in the FITS file should
                   be interpretted as the reciprocal of the noise
                   variance on that visibility.
          blcal    Apply AIPS baseline-dependent calibration to the
                   data.
 
        These options for op=uvout only.
          nocal    Do not apply the gains table to the data.
          nopol    Do not apply the polarization leakage table
                   to the data.
          nopass   Do not apply the bandpass table correctsions
                   to the data.
          topo     Label the frequencies as topocentric. Use this when
                   exporting spectral line data from non doppler tracking
                   arrays like ATCA, EVLA, ALMA, to CASA to get the
                   velocities right.
 
        These options apply for op=xyin only.
          rawdss   Use the conventions for raw Digital Sky Survey FITS
                   files, and convert (partially!) the header. A raw
                   DSS FITS file has header items such as PLTSCALE,
                   XPIXELSZ, YPIXELSZ etc. If you are unsure if your DSS
                   image is raw or conventional FITS, run:
                     Task FITS:
                       in=mydss.fits
                       op=print
                   and look for those header items.  Note that DSS
                   images retrieved using SkyView have a conventional
                   FITS header, and do not require options=rawdss.
          nod2     Use the conventions of NOD2 FITS files.

Key: velocity
        Velocity information. This is only used for op=uvin,
        and is only relevant for line observations.  The default is
        to use the information present in the FITS header.  The
        "velocity" parameter allows this information to be overriden or
        the velocity system to be changed.
 
        Within each line visibility data-set, Miriad stores the velocity
        of the observatory wrt a rest frame.  This allows account to be
        taken of this when determining channel velocities.
 
        The fits task will determine the observatory velocity either by
        being given a velocity at a given channel (wrt a rest frame) or
        by using a model of Earth and solar system motion (accurate to
        5 m/s).
 
        The "velocity" parameter can be used to specify the velocity of
        a particular channel.  The parameter consists of three values:
        the velocity system of the reference value, the reference value
        and the reference channel, viz:
           velocity=velsys,refval,refchan
        Possible values for the velocity system are:
          lsr     Velocity is the radio definition wrt the LSR frame.
          bary    Velocity is the radio definition wrt the barycentre.
          optlsr  Velocity is the optical definition wrt the LSR frame.
          optbary Velocity is the optical definition wrt the barycentre.
          obs     Velocity wrt the observatory.
 
        The reference value gives the velocity, at the reference
        channel, in km/s.  If the reference value and reference channel
        are omitted, a model of Earth and solar system motion is used to
        determine the appropriate information.
 
        For example:
          velocity=lsr,30,1
        indicates that the first channel has radio LSR velocity of
        30 km/s.  The observatory velocity, relative to LSR, can then
        be computed.
 
        Alternately:
          velocity=lsr
        indicates that fits is to determine the observatory velocity
        wrt the LSR frame using an appropriate model.
 
Revision: 1.32, 2014/09/15 04:39:01 UTC

Generated by miriad@atnf.csiro.au on 21 Jun 2016