<!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>Flat Fielding</TITLE> <META NAME="description" CONTENT="Flat Fielding"> <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="node662.html"> <LINK REL="previous" HREF="node660.html"> <LINK REL="up" HREF="node655.html"> <LINK REL="next" HREF="node662.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html9760" HREF="node662.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html9757" HREF="node655.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html9751" HREF="node660.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html9759" 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="tex2html9761" HREF="node662.html">Combining Images</A> <B> Up:</B> <A NAME="tex2html9758" HREF="node655.html">Off-line Reduction</A> <B> Previous:</B> <A NAME="tex2html9752" HREF="node660.html">Sky Subtraction</A> <BR> <BR> <!--End of Navigation Panel--> <H2><A NAME="SECTION003434000000000000000"> </A> <A NAME="irac2:flat-fielding"> </A> <BR> Flat Fielding </H2> Once the flat field has been prepared in the manner described above, the astronomical images may be flat fielded simply by dividing by the flat field. This part of the process is similar to that for optical CCDs. <P> To do the flat fielding in MIDAS, use either <TT>COMPUTE/CCD</TT> to divide the sky subtracted images by the flat field frame, or use the command <TT>FFIELD/IRAC2</TT> to perform the same operation. <P> <BR><HR> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
