<!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 Simplest Case</TITLE> <META NAME="description" CONTENT="The Simplest Case"> <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="node452.html"> <LINK REL="previous" HREF="node450.html"> <LINK REL="up" HREF="node450.html"> <LINK REL="next" HREF="node452.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html7068" HREF="node452.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html7065" HREF="node450.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html7059" HREF="node450.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html7067" 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="tex2html7069" HREF="node452.html">A Case with some</A> <B> Up:</B> <A NAME="tex2html7066" HREF="node450.html">Examples and Hints</A> <B> Previous:</B> <A NAME="tex2html7060" HREF="node450.html">Examples and Hints</A> <BR> <BR> <!--End of Navigation Panel--> <H3><A NAME="SECTION002519100000000000000"> The Simplest Case</A> </H3> <P> This paragraph shows the very simplest possible example of how to do the relative calibration of a CCD-frame. It is assumed that frames are only taken in a single filter (R in this case). The frames available are the following: <UL> <LI>Darks <DL COMPACT> <DT> <BR> <DD>DARK01 is a 20 minute frame taken before/after observing <DT> <BR> <DD>DARK02 <I>dito</I> <DT> <BR> <DD>DARK03 <I>dito</I> <DT> <BR> <DD>DARK04 <I>dito</I> </DL> <LI>Flats <DL COMPACT> <DT> <BR> <DD>FLATR1 20 sec dome flat in R-filter <DT> <BR> <DD>FLATR2 <I>dito</I> <DT> <BR> <DD>FLATR3 <I>dito</I> </DL> <LI>Data <DL COMPACT> <DT> <BR> <DD>N5126R 20 minute exposure of NGC 5126 <DT> <BR> <DD>N7794R 20 minute exposure of NGC 7794 </DL></UL>In order to process these frames, the following commands would be executed.<BLOCKQUOTE> <TT>AVERage/IMAge DARKAV = DARK01,DARK02,DARK03,DARK04 <BR> AVERage/IMAge FLATAV = FLATR1,FLATR2,FLATR3 <BR> COMPute/IMAge DENOM = FLATAV-DARKAV <BR> COMPute/IMAge N5126RF = (N5126R-DARKAV)/DENOM <BR> COMPute/IMAge N7794RF = (N7794R-DARKAV)/DENOM</TT></BLOCKQUOTE>The first two commands compute the simple averages of the dark and flat field images. The third command computes the dark subtracted average flat field. The final two commands perform the flat fielding of the data frames. Note that there has been no correction for bad columns in either the flat field, the dark frames or the data frames. The next example shows how to do this. <P> <HR> <!--Navigation Panel--> <A NAME="tex2html7068" HREF="node452.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html7065" HREF="node450.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html7059" HREF="node450.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html7067" 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="tex2html7069" HREF="node452.html">A Case with some</A> <B> Up:</B> <A NAME="tex2html7066" HREF="node450.html">Examples and Hints</A> <B> Previous:</B> <A NAME="tex2html7060" HREF="node450.html">Examples and Hints</A> <!--End of Navigation Panel--> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
