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Basic Information on 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
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:
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
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 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.
indicates that the first channel has radio LSR velocity of
30 km/s. The observatory velocity, relative to LSR, can then
indicates that fits is to determine the observatory velocity
wrt the LSR frame using an appropriate model.
Revision: 1.27, 2013/03/21 21:08:16 UTC
Generated by firstname.lastname@example.org on 22 Mar 2013