<!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>The Reduction Session</TITLE> <META NAME="description" CONTENT="The Reduction Session"> <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="node476.html"> <LINK REL="previous" HREF="node467.html"> <LINK REL="up" HREF="node455.html"> <LINK REL="next" HREF="node469.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html7285" HREF="node469.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html7282" HREF="node455.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html7276" HREF="node467.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html7284" 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="tex2html7286" HREF="node469.html">Reduction using Standard Stars</A> <B> Up:</B> <A NAME="tex2html7283" HREF="node455.html">Echelle Reduction</A> <B> Previous:</B> <A NAME="tex2html7277" HREF="node467.html">Session Parameters</A> <BR> <BR> <!--End of Navigation Panel--> <H1><A NAME="SECTION0027100000000000000000"> The Reduction Session</A> </H1> <P> The reduction session consists of the following steps: <P> <UL> <LI>Order definition: defines the orders location, usually from a Flat-Field <LI>Wavelength calibration <LI>Flat-Field correction <LI>Correction for the response curve <LI>Reduction of science spectra </UL> <P> Flat-field correction is optional as well as response curve correction, but instrumental effects show up as large variations on varying scales. There are two possibilities: either you have a standard star (STD) or you don't. If you did not take a STD exposure, because you were not interested in an absolute or relative flux calibration, you will now have serious problems in producing an acceptable spectrum. There are correction methods for the instrumental response with no standard star but they do not always provide a satisfactory solution and are time consuming. <P> A summary of the different operations performed by commands <TT>RESPONSE/ECHELLE</TT> and <TT>REDUCE/ECHELLE</TT> is provided in <A HREF="node478.html#echelle_reduction_summary">D.13</A>. <P> <BR><HR> <!--Table of Child-Links--> <A NAME="CHILD_LINKS"> </A> <UL> <LI><A NAME="tex2html7287" HREF="node469.html">Reduction using Standard Stars</A> <UL> <LI><A NAME="tex2html7288" HREF="node470.html">Order Definition: Methods STD and COM</A> <LI><A NAME="tex2html7289" HREF="node471.html">Order definition: Method Hough</A> <LI><A NAME="tex2html7290" HREF="node472.html">Wavelength calibration</A> <LI><A NAME="tex2html7291" HREF="node473.html">Background Correction</A> <LI><A NAME="tex2html7292" HREF="node474.html">Flat Field correction</A> </UL> <LI><A NAME="tex2html7293" HREF="node475.html">Reduction without Standard Star</A> </UL> <!--End of Table of Child-Links--> <BR><HR> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
