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<H2><A NAME="SECTION002321000000000000000">
<TT>ASTROMET/TRANSFORM</TT></A>
</H2>
This command computes the astrometric transformation parameters for
the input data set using a least-square fitting algorithm. The input
data is assumed to be two MIDAS tables with fixed columns names. The accuracy
has been tested on standard stars, and in real life on many objects
including comet Shoemaker-Levy 9, leading to very accurate impact
times. <TT>ASTROMET/TRANSFORM</TT> only computes the transformation
parameters. Other commands (see below) should be used to actually
do the transformations, to edit the data, or to display the residuals.
<P>
The first input MIDAS table should contain the coordinates of the
standard stars in RA and Dec. It should contain the following columns:
<UL>
<LI><TT>:PPM</TT> Integer column (I6) containing the identifier
of the standards;
<LI><TT>:R_A</TT> Real column containing the right ascension in
degrees;
<LI><TT>:DEC</TT> Real column with the declination in degrees;
<LI><TT>:MAG</TT> Real column with the magnitude;
<LI><TT>:PMA</TT> Real column with the proper motion in RA in
arcsec/year (NOT time_second);
<LI><TT>:PMD</TT> Real column with the proper motion in Dec in
arcsec/year.
</UL>A possible way to produce this table is to use StarCat, with the
MIDAS table output option, in the PPM catalogue.
<P>
The second MIDAS table should contain the XY measurements of the
standards and should have, as a minimum, the following columns:
<UL>
<LI><TT>:IDENT</TT> Character columns (A16) which must contain a
character string; leading letters (<I>e.g.</I>
PPM) are ignored;
<LI><TT>:XCEN</TT> Real column to contain the X measurement;
<LI><TT>:YCEN</TT> Real column to contain the Y measurement.
</UL>
<P>
The remaining parameters are: the coordinate of the center, the
epoch of the plate and the reference epoch of the catalogue,
two instruments flag, a tolerance on the measurements, and a
selection flag. These parameters are described in the help file
of the command (<TT>HELP ASTROMET/TRANSFORM</TT>).
<P>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-15</I>
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