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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