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diff --git a/src/slalib/sun67.htx/node205.html b/src/slalib/sun67.htx/node205.html new file mode 100644 index 0000000..6da5021 --- /dev/null +++ b/src/slalib/sun67.htx/node205.html @@ -0,0 +1,92 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<!--Converted with LaTeX2HTML 97.1 (release) (July 13th, 1997) + 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 Lippman, Marek Rouchal, Martin Wilck and others --> +<HTML> +<HEAD> +<TITLE>Mean Places</TITLE> +<META NAME="description" CONTENT="Mean Places"> +<META NAME="keywords" CONTENT="sun67"> +<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="sun67.css"> +<LINK REL="next" HREF="node206.html"> +<LINK REL="previous" HREF="node203.html"> +<LINK REL="up" HREF="node197.html"> +<LINK REL="next" HREF="node206.html"> +</HEAD> +<BODY > +<BR> <HR> +<A NAME="tex2html2501" HREF="node206.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html2499" HREF="node197.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html2493" HREF="node204.html"> +<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="previous_motif.gif"></A> <A HREF="sun67.html#stardoccontents"><IMG ALIGN="BOTTOM" BORDER="0" + SRC="contents_motif.gif"></A> +<BR> +<B> Next:</B> <A NAME="tex2html2502" HREF="node206.html">Epoch</A> +<BR> +<B>Up:</B> <A NAME="tex2html2500" HREF="node197.html">EXPLANATION AND EXAMPLES</A> +<BR> +<B> Previous:</B> <A NAME="tex2html2494" HREF="node204.html">SLALIB support for precession and nutation</A> +<BR> <HR> <P> +<P><!--End of Navigation Panel--> +<H2><A NAME="SECTION00055000000000000000"> +Mean Places</A> +</H2> +The main effect of the precession/nutation is a steady increase of about +<IMG WIDTH="25" HEIGHT="18" ALIGN="BOTTOM" BORDER="0" + SRC="img261.gif" + ALT="$50\hspace{-0.05em}^{'\hspace{-0.1em}'}$">/year in the ecliptic longitudes of the stars. It is therefore +essential, when reporting the position of an astronomical target, to +qualify the coordinates with a date, or <I>epoch</I>. +Specifying the epoch ties down the equator and +equinox which define the <IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$"> coordinate system that is +being used. +<A NAME="tex2html5" HREF="footnode.html#27903"><SUP><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="foot_motif.gif"></SUP></A> For simplicity, only +the smooth and steady ``general +precession'' part of the complete precession/nutation effect is +included, thereby defining what is called the <I>mean</I> +equator and equinox for the epoch concerned. We say a star +has a mean place of (for example) +<IMG WIDTH="104" HEIGHT="17" ALIGN="BOTTOM" BORDER="0" + SRC="img262.gif" + ALT="$12^{h}\,07^{m}\,58^{s}.09$"> <IMG WIDTH="102" HEIGHT="35" ALIGN="MIDDLE" BORDER="0" + SRC="img263.gif" + ALT="$-19^{\circ}\,44^{'}\,37^{''}.1$"> ``with respect to the mean equator +and equinox of epoch J2000''. The short way of saying +this is ``<IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$"> equinox J2000'' (<B>not</B> ``<IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$"> epoch J2000'', +which means something different to do with +proper motion). +<P> +<BR> <HR> +<A NAME="tex2html2501" HREF="node206.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html2499" HREF="node197.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html2493" HREF="node204.html"> +<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="previous_motif.gif"></A> <A HREF="sun67.html#stardoccontents"><IMG ALIGN="BOTTOM" BORDER="0" + SRC="contents_motif.gif"></A> +<BR> +<B> Next:</B> <A NAME="tex2html2502" HREF="node206.html">Epoch</A> +<BR> +<B>Up:</B> <A NAME="tex2html2500" HREF="node197.html">EXPLANATION AND EXAMPLES</A> +<BR> +<B> Previous:</B> <A NAME="tex2html2494" HREF="node204.html">SLALIB support for precession and nutation</A> +<BR> <HR> <P> +<P><!--End of Navigation Panel--> +<ADDRESS> +<I>SLALIB --- Positional Astronomy Library<BR>Starlink User Note 67<BR>P. T. Wallace<BR>12 October 1999<BR>E-mail:ptw@star.rl.ac.uk</I> +</ADDRESS> +</BODY> +</HTML> |