<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <!--Converted with LaTeX2HTML 98.1p1 release (March 2nd, 1998) originally by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds * revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan * with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --> <HTML> <HEAD> <TITLE>Order definition</TITLE> <META NAME="description" CONTENT="Order definition"> <META NAME="keywords" CONTENT="vol2"> <META NAME="resource-type" CONTENT="document"> <META NAME="distribution" CONTENT="global"> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <LINK REL="STYLESHEET" HREF="vol2.css"> <LINK REL="next" HREF="node701.html"> <LINK REL="previous" HREF="node699.html"> <LINK REL="up" HREF="node696.html"> <LINK REL="next" HREF="node701.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html10242" HREF="node701.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html10239" HREF="node696.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html10233" HREF="node699.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html10241" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="icons.gif/contents_motif.gif"></A> <BR> <B> Next:</B> <A NAME="tex2html10243" HREF="node701.html">Background subtraction</A> <B> Up:</B> <A NAME="tex2html10240" HREF="node696.html">FEROS</A> <B> Previous:</B> <A NAME="tex2html10234" HREF="node699.html">Requirement for the FEROS</A> <BR> <BR> <!--End of Navigation Panel--> <H1><A NAME="SECTION003740000000000000000"> Order definition</A> </H1> <P> Due to the use of an image slicer for the two fibers, the FEROS order definition uses a special technique for finding and centering orders. The definition of the orders is done in several steps. <P> <UL> <LI> First, the position of the orders is defined near the middle of the frame. A central cut through the orders is cross-correlated with a template which should match as good as possible the cross-order profile. Centering the peaks of the correlation function gives the centers of the orders near the center of the CCD. If the template consists of the profile of a double fiber, both fibers are centered simultaneously. This is the normal way of operation. <LI> Second, the orders are followed along the main dispersion direction by cross-correlating cuts taken at varying y-positions with a secondary template extracted from the central cut. <LI> Finally, the detected x-y positions of all orders are fitted with a polynomial. This is done for each order individually. The polynomial coefficients are kept in a table for the further steps. </UL> <P> Order definition is done with the command DEFINE/FEROS. <P> <HR> <!--Navigation Panel--> <A NAME="tex2html10242" HREF="node701.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html10239" HREF="node696.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html10233" HREF="node699.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html10241" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="icons.gif/contents_motif.gif"></A> <BR> <B> Next:</B> <A NAME="tex2html10243" HREF="node701.html">Background subtraction</A> <B> Up:</B> <A NAME="tex2html10240" HREF="node696.html">FEROS</A> <B> Previous:</B> <A NAME="tex2html10234" HREF="node699.html">Requirement for the FEROS</A> <!--End of Navigation Panel--> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
