<!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>General instrumental information</TITLE> <META NAME="description" CONTENT="General instrumental information"> <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="node608.html"> <LINK REL="previous" HREF="node606.html"> <LINK REL="up" HREF="node605.html"> <LINK REL="next" HREF="node608.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html9112" HREF="node608.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html9109" HREF="node605.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html9103" HREF="node606.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html9111" 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="tex2html9113" HREF="node608.html">Passbands</A> <B> Up:</B> <A NAME="tex2html9110" HREF="node605.html">Instrument configuration and run-specific</A> <B> Previous:</B> <A NAME="tex2html9104" HREF="node606.html">Storage format</A> <BR> <BR> <!--End of Navigation Panel--> <H2><A NAME="SECTION003252000000000000000"> General instrumental information</A> </H2> The two principal classes of information needed about photometric instruments concern filters and detectors. We need two kinds of information for filters and detectors: physical information about the instrument itself, and logical information about the way it is represented in data files - for example, the codes used to identify filter positions. <P> In addition, it is useful to know the condition of the telescope optics: clean optics give not only better signal/noise ratio than dirty ones, but also more stable zero-points from night to night. Sometimes it is possible to have the optics cleaned before a critical observing run; observers should consider this possibility. <P> Some, but by no means all, of the required information is available in the ESO Archive - mostly in the archive log files [<A HREF="node649.html#E92">5</A>]. This can be stripped out and used when it is available; when it is not, the observer will have to supply the information. <P> In addition to information about the instrument itself, the reduction program needs to know the structure of the data in their table file (see section <A HREF="node633.html#sect-data">I.6</A>, ``Observational data''). Thus, you must make sure that information such as the number of filter-code columns and the filter codes that correspond to particular passbands, which is in the instrument-description table, agrees with the actual data tables. Usually, this is determined by the program that converts raw data files to table format. <P> <HR> <!--Navigation Panel--> <A NAME="tex2html9112" HREF="node608.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html9109" HREF="node605.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html9103" HREF="node606.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html9111" 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="tex2html9113" HREF="node608.html">Passbands</A> <B> Up:</B> <A NAME="tex2html9110" HREF="node605.html">Instrument configuration and run-specific</A> <B> Previous:</B> <A NAME="tex2html9104" HREF="node606.html">Storage format</A> <!--End of Navigation Panel--> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
