<!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>Bias, Dark and Flat Field Correction</TITLE> <META NAME="description" CONTENT="Bias, Dark and Flat Field Correction"> <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="previous" HREF="node53.html"> <LINK REL="up" HREF="node52.html"> <LINK REL="next" HREF="node55.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html2109" HREF="node55.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html2106" HREF="node52.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html2102" HREF="node53.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html2108" 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="tex2html2110" HREF="node55.html">Additional Processing</A> <B> Up:</B> <A NAME="tex2html2107" HREF="node52.html">Running REDUCE/CCD</A> <B> Previous:</B> <A NAME="tex2html2103" HREF="node53.html">Overscan correction and trimming</A> <BR> <BR> <!--End of Navigation Panel--> <H3><A NAME="SECTION00692200000000000000"> Bias, Dark and Flat Field Correction</A> </H3> This part has already been discussed in Section <A HREF="node42.html#ccd:preparing-your-calibration-frames">3.8</A>. Depending on the keywords <TT>SC_BSCOR</TT>, <TT>SC_DKCOR</TT>, and <TT>SC_FFCOR</TT> the calibration procedure checks for the availability of the master bias, dark, and flat field calibration frames. If they can not be found they will be created using the input frames listed in the Association Table, and according to the keyword setting for combining. <P> The next step after having obtained the calibration frames is to process these frames. For example, after the flat is created/found it will be checked for its processing status. If it has not been processed any on-going calibration (<I>i.e.</I> of a science frame) will be interrupted, and the flat field will be processed. After this has been completed processing of the science frame will continue. <P> <BR><HR> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
