<!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>Telescope optics</TITLE> <META NAME="description" CONTENT="Telescope optics"> <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="node628.html"> <LINK REL="previous" HREF="node619.html"> <LINK REL="up" HREF="node605.html"> <LINK REL="next" HREF="node628.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html9342" HREF="node628.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html9339" HREF="node605.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html9333" HREF="node626.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html9341" 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="tex2html9343" HREF="node628.html">Sample instrument files</A> <B> Up:</B> <A NAME="tex2html9340" HREF="node605.html">Instrument configuration and run-specific</A> <B> Previous:</B> <A NAME="tex2html9334" HREF="node626.html">Other detectors: DET=OTHER</A> <BR> <BR> <!--End of Navigation Panel--> <H2><A NAME="SECTION003256000000000000000"> Telescope optics</A> </H2> Finally, the condition of the telescope optics should be stored in a character descriptor named <B>CONDITION</B> in the instrumental ``.tbl'' file. Possible values are <TT>'CLEAN'</TT>, if the mirrors have been re-coated or cleaned within two weeks of the observing run, and/or a flashlight beam is barely visible on optical surfaces; <TT>'AVERAGE'</TT>, if a flashlight beam is plainly visible on the optical surface, but the dirt is not very bad; and <TT>'DIRTY'</TT>, if shining a flashlight beam on the primary produces a sensation of revulsion in a trained observer. Obviously, some experience is required to judge these categories accurately. <P> <BR><HR> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
