<!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>Star tables</TITLE> <META NAME="description" CONTENT="Star tables"> <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="node260.html"> <LINK REL="previous" HREF="node253.html"> <LINK REL="up" HREF="node253.html"> <LINK REL="next" HREF="node255.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html4617" HREF="node255.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html4614" HREF="node253.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html4608" HREF="node253.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html4616" 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="tex2html4618" HREF="node255.html">ASCII source files</A> <B> Up:</B> <A NAME="tex2html4615" HREF="node253.html">Getting started</A> <B> Previous:</B> <A NAME="tex2html4609" HREF="node253.html">Getting started</A> <BR> <BR> <!--End of Navigation Panel--> <H2><A NAME="SECTION001821000000000000000"> </A> <A NAME="startables"> </A> <BR> Star tables </H2> The essential data needed for program stars are names, positions, and the equinox to which the positions are referred. You may also include proper motions and the epoch of the position; spectral types; rough magnitudes, such as might be obtained from the HD; and comments. The command <TT>MAKE/STARTABLE</TT> helps you create a table of program stars. <P> Some telescopes record the position toward which the control system thinks the telescope is pointing as part of the data stream, so it is tempting to extract these data to make a positional catalog for the program stars. In general, this is very unwise. The telescopes usually used for photometry generally have neither accurate nor precise pointing. <P> The <I>precision</I> (repeatability) of the recorded positions does not indicate their <I>accuracy</I> -- which could be far worse, if the observer adjusted the zero-points of the telescope's coordinates to agree with mean places for some equinox removed a few years in time from the date of observations. A 2' altitude error corresponds to an airmass error of 0.002 at 2 airmasses, more than 0.005 at 3 airmasses, and 0.01 airmass at 4 airmasses. Thus, such errors can cause appreciable systematic errors in extinction determination and correction. Although such recorded positions are available (by means of the CONVERT/PHOT command) as a last resort, they are <I>not</I> recommended. Good catalog positions should be used whenever they are available. <P> Standard-star tables also require columns for the standard values, which are often not known for program stars. Because of this difference in content, you should keep standard and program stars in separate table files. You can have several files of each type. The programs will ask for the standard-star files first, and then the program-star files. <P> You should also plan to keep extinction stars (and other constant objects, such as comparison stars in variable-star programs) in a <I>separate</I> file from variable stars. The reduction program treats standard, constant, and variable stars differently, so each group should be kept in one or more separate files (see subsection <A HREF="node285.html#reductionproc">13.5.6</A>, ``Reduction procedure''). <P> <BR><HR> <!--Table of Child-Links--> <A NAME="CHILD_LINKS"> </A> <UL> <LI><A NAME="tex2html4619" HREF="node255.html">ASCII source files</A> <LI><A NAME="tex2html4620" HREF="node256.html">Format files</A> <LI><A NAME="tex2html4621" HREF="node257.html">Manual entry of data</A> <LI><A NAME="tex2html4622" HREF="node258.html">Multiple star files</A> <LI><A NAME="tex2html4623" HREF="node259.html">Standard-star files</A> </UL> <!--End of Table of Child-Links--> <HR> <!--Navigation Panel--> <A NAME="tex2html4617" HREF="node255.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html4614" HREF="node253.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html4608" HREF="node253.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html4616" 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="tex2html4618" HREF="node255.html">ASCII source files</A> <B> Up:</B> <A NAME="tex2html4615" HREF="node253.html">Getting started</A> <B> Previous:</B> <A NAME="tex2html4609" HREF="node253.html">Getting started</A> <!--End of Navigation Panel--> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
