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| author | Joseph Hunkeler <jhunkeler@gmail.com> | 2015-03-04 21:21:30 -0500 |
|---|---|---|
| committer | Joseph Hunkeler <jhunkeler@gmail.com> | 2015-03-04 21:21:30 -0500 |
| commit | d54fe7c1f704a63824c5bfa0ece65245572e9b27 (patch) | |
| tree | afc52015ffc2c74e0266653eecef1c8ef8ba5d91 /src/slalib/sun67.htx/node207.html | |
| download | calfuse-d54fe7c1f704a63824c5bfa0ece65245572e9b27.tar.gz | |
Initial commit
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| -rw-r--r-- | src/slalib/sun67.htx/node207.html | 119 |
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diff --git a/src/slalib/sun67.htx/node207.html b/src/slalib/sun67.htx/node207.html new file mode 100644 index 0000000..6c74c4e --- /dev/null +++ b/src/slalib/sun67.htx/node207.html @@ -0,0 +1,119 @@ +<!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>Proper Motion</TITLE> +<META NAME="description" CONTENT="Proper Motion"> +<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="node208.html"> +<LINK REL="previous" HREF="node206.html"> +<LINK REL="up" HREF="node197.html"> +<LINK REL="next" HREF="node208.html"> +</HEAD> +<BODY > +<BR> <HR> +<A NAME="tex2html2521" HREF="node208.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html2519" HREF="node197.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html2513" HREF="node206.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="tex2html2522" HREF="node208.html">Parallax and Radial Velocity</A> +<BR> +<B>Up:</B> <A NAME="tex2html2520" HREF="node197.html">EXPLANATION AND EXAMPLES</A> +<BR> +<B> Previous:</B> <A NAME="tex2html2514" HREF="node206.html">Epoch</A> +<BR> <HR> <P> +<P><!--End of Navigation Panel--> +<H2><A NAME="SECTION00057000000000000000"> +Proper Motion</A> +</H2> +Stars in catalogues usually have, in addition to the +<IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$"> coordinates, a <I>proper motion</I> <IMG WIDTH="54" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img264.gif" + ALT="$[\mu_\alpha,\mu_\delta]$">.This is an intrinsic motion +of the star across the background. Very few stars have a +proper motion which exceeds <IMG WIDTH="17" HEIGHT="17" ALIGN="BOTTOM" BORDER="0" + SRC="img140.gif" + ALT="$1\hspace{-0.05em}^{'\hspace{-0.1em}'}$">/year, and most are +far below this level. A star observed as part of normal +astronomy research will, as a rule, have a proper motion +which is unknown. +<P> +Mean <IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$"> and rate of change are not sufficient to pin +down a star; the epoch at which the <IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$"> was or will +be correct is also needed. Note the distinction +between the epoch which specifies the +coordinate system and the epoch at which the star passed +through the given <IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$">. The full specification for a star +is <IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$">, proper motions, equinox and epoch (plus something to +identify which set of models for the precession <I>etc.</I> is +being used - see the next section). +For convenience, coordinates given in star catalogues are almost +always adjusted to make the equinox and epoch the same - for +example B1950 in the case of the SAO catalogue. +<P> +SLALIB provides one routine to handle proper motion on its own, +sla_PM. +Proper motion is also allowed for in various other +routines as appropriate, for example +sla_MAP +and +sla_FK425. +Note that in all SLALIB routines which involve proper motion +the units are radians per year and the +<IMG WIDTH="13" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img24.gif" + ALT="$\alpha$"> component is in the form <IMG WIDTH="13" HEIGHT="13" ALIGN="BOTTOM" BORDER="0" + SRC="img115.gif" + ALT="$\dot{\alpha}$"> (<I>i.e.</I> big +numbers near the poles). +Some star catalogues have proper motion per century, and +in some catalogues the <IMG WIDTH="13" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img24.gif" + ALT="$\alpha$"> component is in the form +<IMG WIDTH="48" HEIGHT="13" ALIGN="BOTTOM" BORDER="0" + SRC="img116.gif" + ALT="$\dot{\alpha}\cos\delta$"> (<I>i.e.</I> angle on the sky). +<P> +<BR> <HR> +<A NAME="tex2html2521" HREF="node208.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html2519" HREF="node197.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html2513" HREF="node206.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="tex2html2522" HREF="node208.html">Parallax and Radial Velocity</A> +<BR> +<B>Up:</B> <A NAME="tex2html2520" HREF="node197.html">EXPLANATION AND EXAMPLES</A> +<BR> +<B> Previous:</B> <A NAME="tex2html2514" HREF="node206.html">Epoch</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> |