<!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>Moving objects</TITLE> <META NAME="description" CONTENT="Moving objects"> <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="node565.html"> <LINK REL="up" HREF="node554.html"> <LINK REL="next" HREF="node567.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html8592" HREF="node567.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html8589" HREF="node554.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html8585" HREF="node565.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html8591" 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="tex2html8593" HREF="node567.html">UT date </A> <B> Up:</B> <A NAME="tex2html8590" HREF="node554.html">Star tables</A> <B> Previous:</B> <A NAME="tex2html8586" HREF="node565.html">Standard values</A> <BR> <BR> <!--End of Navigation Panel--> <H2><A NAME="SECTION003224000000000000000"> Moving objects</A> </H2> For moving objects such as asteroids, comets, or planets, it is useful to include ephemeris information, both to provide predicted coordinates for planning observations, and to allow accurate airmass calculations in the reductions. Each such object requires several positions, each associated with a time. These times can be given either as Modified Julian Dates ( <!-- MATH: $MJD = JD - 2400000.5$ --> <I>MJD</I> = <I>JD</I> - 2400000.5), or as ordinary date strings like <TT>1995 Jan 23.0</TT>. To allow good interpolation, include two ephemeris entries before and two after the interval of observations. The tabular interval need not be one day, but can have any constant value from one table entry to the next. <P> <BR><HR> <!--Table of Child-Links--> <A NAME="CHILD_LINKS"> </A> <UL> <LI><A NAME="tex2html8594" HREF="node567.html">UT date -- column label: DATE</A> <LI><A NAME="tex2html8595" HREF="node568.html">MJD -- column label: MJD_OBS</A> </UL> <!--End of Table of Child-Links--> <BR><HR> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
