<!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>Extinction and transformation models</TITLE> <META NAME="description" CONTENT="Extinction and transformation models"> <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="node285.html"> <LINK REL="previous" HREF="node279.html"> <LINK REL="up" HREF="node271.html"> <LINK REL="next" HREF="node281.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html4938" HREF="node281.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html4935" HREF="node271.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html4929" HREF="node279.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html4937" 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="tex2html4939" HREF="node281.html">The bias problem</A> <B> Up:</B> <A NAME="tex2html4936" HREF="node271.html">Reducing the observations</A> <B> Previous:</B> <A NAME="tex2html4930" HREF="node279.html">Choosing a gradient estimator</A> <BR> <BR> <!--End of Navigation Panel--> <H2><A NAME="SECTION001855000000000000000"> Extinction and transformation models</A> </H2> <P> To determine the parameters we want (stellar magnitudes and colors) from the observations we have, we fit the data to a model. The model should represent the circumstances of the observations as realistically as possible; otherwise, effects present in the data but not in the model will be distributed among the available adjustable parameters, such as stellar magnitudes, extinction coefficients, and transformation parameters. The result may well be a good fit to the data, with small residuals; but the parameters will be biased -- that is, they will have significant systematic errors. Such errors are called <I>reduction errors</I> by Manfroid and Sterken [<A HREF="node307.html#MS92">16</A>] <P> <BR><HR> <!--Table of Child-Links--> <A NAME="CHILD_LINKS"> </A> <UL> <LI><A NAME="tex2html4940" HREF="node281.html">The bias problem</A> <LI><A NAME="tex2html4941" HREF="node282.html">Equations of condition</A> <LI><A NAME="tex2html4942" HREF="node283.html">Strategy</A> <LI><A NAME="tex2html4943" HREF="node284.html">Standard stars</A> </UL> <!--End of Table of Child-Links--> <BR><HR> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
