Content-type: text/html Manpage of fits


Section: User Commands (1)
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fits - Conversion between Miriad and FITS image and uv formats  




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!


  For a description of the standard, see


Name of the input file (either a FITS or Miriad file name, depending on OP). No default.
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.
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.
Line type of the output, when op=uvout. This is of the form:


"Linetype" is either "channel", "wide" or "velocity". "Nchan" is the number of channels in the output.

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
Normal uv selection, used when op=uvout.
Normal Stokes selection, used when op=uvout
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

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.

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:
           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.
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:

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 barycenter.
  optlsr  Velocity is the optical definition wrt the LSR frame.
  optbary Velocity is the optical definition wrt the barycenter.
  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:

indicates that the first channel has radio LSR velocity of 30 km/s. The observatory velocity, relative to LSR, can then be computed.


indicates that fits is to determine the observatory velocity wrt the LSR frame using an appropriate model.

ts.for,v 1.19 2011/06/10 11:42:42 pteuben Exp $




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Time: 18:35:38 GMT, July 05, 2011