<!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>Introduction</TITLE> <META NAME="description" CONTENT="Introduction"> <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="node122.html"> <LINK REL="previous" HREF="node120.html"> <LINK REL="up" HREF="node120.html"> <LINK REL="next" HREF="node122.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html2966" HREF="node122.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html2963" HREF="node120.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html2957" HREF="node120.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html2965" 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="tex2html2967" HREF="node122.html">Photometric Corrections</A> <B> Up:</B> <A NAME="tex2html2964" HREF="node120.html">Long-Slit and 1D Spectra</A> <B> Previous:</B> <A NAME="tex2html2958" HREF="node120.html">Long-Slit and 1D Spectra</A> <BR> <BR> <!--End of Navigation Panel--> <H1><A NAME="SECTION001010000000000000000"> Introduction</A> </H1> <P> This chapter describes the long-slit<A NAME="5703"> </A> reduction package in a general way. One-dimensional spectra are considered to be a particular case of long-slit spectra and are also handled by the package. More instrument-specific operating instructions may be given in appendices to this MIDAS manual or in the relevant ESO Instrument Handbooks. <P> The package provides about 50 basic commands to perform the calibration and to display the results, defined in the context <TT>LONG</TT>. A tutorial<A NAME="5705"> </A> procedure, <TT>TUTORIAL/LONG</TT>, illustrates how to operate the package. The context <TT>SPEC</TT> is a low-level context including general utility commands required by the different spectroscopy packages <TT>ECHELLE</TT>, <TT>IRSPEC</TT> and <TT>LONG</TT>. These commands are refered to and summarized in this chapter. The graphical user interface<A NAME="5711"> </A><A NAME="5712"> </A> <TT>XLong</TT> is a MOTIF-based interface providing an easy access to the commands of the package. This interface is described in the Appendix <A HREF="node497.html#long_slit_spectra">G</A>. Standard spectral analysis<A NAME="5715"> </A> can be performed with the graphical user interface <TT>XAlice</TT> (command <TT>CREATE/GUI ALICE</TT>). The use of general MIDAS commands for spectral analysis is also discussed in this chapter. <P> The main characteristics of the <TT>LONG</TT> context are derived from its modularity, that allows to perform, in a first step, the image cosmetics and photometric corrections - which are detector dependent - and then, to correct for the geometric distortions. The method gives particular emphasis to an accurate wavelength calibration<A NAME="5719"> </A> and correction of all distortions along the whole slit, so that the spatial structure of extended objects can be examined in detail. <P> Although the method is applicable to different instrumental configurations, we assume, in the following description, that the generic instrument consists of a spectrograph coupled to a CCD detector. In the current version it is assumed that the CCD frame is oriented with the rows in the dispersion direction and the columns along the slit. <P> <BLOCKQUOTE> <DIV ALIGN="CENTER"> <B>Note</DIV> <I>This chapter only provides a synopsis of the commands needed for the reduction of long-slit. It is important to realise that it can neither substitute the <TT>HELP</TT> information available for each command nor be exhaustive, especially not with regard to the usage of general utilities such as the MIDAS Table System, the AGL Graphics package, <I>etc.</I> The Appendix <A HREF="node497.html#long_slit_spectra">G</A> provides a practical approach to the reduction of long-slit spectra.</I></B></BLOCKQUOTE> <P> <HR> <!--Navigation Panel--> <A NAME="tex2html2966" HREF="node122.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html2963" HREF="node120.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html2957" HREF="node120.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html2965" 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="tex2html2967" HREF="node122.html">Photometric Corrections</A> <B> Up:</B> <A NAME="tex2html2964" HREF="node120.html">Long-Slit and 1D Spectra</A> <B> Previous:</B> <A NAME="tex2html2958" HREF="node120.html">Long-Slit and 1D Spectra</A> <!--End of Navigation Panel--> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
