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<H2><A NAME="SECTION002783000000000000000">
Standard orientation</A>
</H2>
<P>
The frames, as they appear on the monitor with the command <TT>LOAD/IMAGE</TT>,
are in general not oriented properly. All reduction programs assume that on
the monitor the wavelength increases from left to right and that the spectral
orders increase from top to bottom. This means that the frames have to
be rotated in such a way that:
<P>
<UL>
<LI>orders are more or less horizontal, but slightly climbing from
left to right.
<LI>orders separation are narrower at the bottom than at the top.
</UL>
<P>
The images have to be rotated, depending on the way the CCD chip has been
mounted. To do this, prepare again a catalogue containing all files which
have to be rotated using <TT>CREATE/ICAT</TT>. Next run the program
<P>
<BLOCKQUOTE>
<TT>ROTATE/ECHELLE inputspec outframe mode</TT></BLOCKQUOTE>
<P>
<BLOCKQUOTE>
<DIV ALIGN="CENTER">
<B>Note</DIV>
<I>The rotation is usually required for <TT>CASPEC, EFOSC, ECHELLEC,</TT>
and <TT>EMMI</TT> spectra. The command <TT>ROTATE/ECHELLE</TT>
sets descriptor values <TT>START and STEP</TT> to 1.,1. for all images
and updates the session keyword <TT>CCDBIN</TT> to the original steps
of the images. These operations must be performed by the user if another
command than <TT>ROTATE/ECHELLE</TT> is applied.</I></B></BLOCKQUOTE>
<P>
As in <TT>PREPARE/WINDOW</TT>, <TT>inputspec</TT> is either a single input frame or a
catalogue; <TT>outframe</TT> is either a single output frame or a two character
identifier which will replace the first two characters of the name of each
input frame; mode decides if the images are just rotated over -90 degrees (mode
<TT>ROTATE</TT>, data obtained before April 1984) or rotated over 90 degrees and
flipped in the <I>x</I>-direction (mode <TT>FLIP</TT>) for frames obtained later. This
command will also read the exposure time from the descriptor <TT>O_TIME</TT>,
prompting for it if the descriptor is not present.
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-15</I>
</ADDRESS>
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