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diff --git a/src/slalib/sun67.htx/node78.html b/src/slalib/sun67.htx/node78.html new file mode 100644 index 0000000..61458ac --- /dev/null +++ b/src/slalib/sun67.htx/node78.html @@ -0,0 +1,168 @@ +<!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>SLA_DTPS2C - Plate centre from and </TITLE> +<META NAME="description" CONTENT="SLA_DTPS2C - Plate centre from and "> +<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="node79.html"> +<LINK REL="previous" HREF="node77.html"> +<LINK REL="up" HREF="node13.html"> +<LINK REL="next" HREF="node79.html"> +</HEAD> +<BODY > +<BR> <HR> +<A NAME="tex2html1206" HREF="node79.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html1204" HREF="node13.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html1198" HREF="node77.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="tex2html1207" HREF="node79.html">SLA_DTPV2C - Plate centre from and x,y,z</A> +<BR> +<B>Up:</B> <A NAME="tex2html1205" HREF="node13.html">SUBPROGRAM SPECIFICATIONS</A> +<BR> +<B> Previous:</B> <A NAME="tex2html1199" HREF="node77.html">SLA_DTP2V - Tangent Plane to Direction Cosines</A> +<BR> <HR> <P> +<P><!--End of Navigation Panel--> +<H2><A NAME="SECTION000465000000000000000"> </A><A NAME="xref_SLA_DTPS2C"> </A><A NAME="SLA_DTPS2C"> </A> +<BR> +SLA_DTPS2C - Plate centre from <IMG WIDTH="26" HEIGHT="27" ALIGN="MIDDLE" BORDER="0" + SRC="img90.gif" + ALT="$\xi,\eta$"> and <IMG WIDTH="28" HEIGHT="27" ALIGN="MIDDLE" BORDER="0" + SRC="img91.gif" + ALT="$\alpha,\delta$"></H2> + <DL> +<DT><STRONG>ACTION:</STRONG> +<DD>From the tangent plane coordinates of a star of known <IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$">,determine the <IMG WIDTH="42" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img3.gif" + ALT="$[\,\alpha,\delta\,]$"> of the tangent point (double precision) +<P> <DT><STRONG>CALL:</STRONG> +<DD><TT>CALL sla_DTPS2C (XI, ETA, RA, DEC, RAZ1, DECZ1, RAZ2, DECZ2, N)</TT> +<P> </DL> +<P> <DL> +<DT><STRONG>GIVEN:</STRONG> +<DD> +<BR> +<TABLE CELLPADDING=3> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>XI,ETA</EM></TD> +<TH ALIGN="LEFT"><B>D</B></TH> +<TD ALIGN="LEFT" NOWRAP>tangent plane rectangular coordinates (radians)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>RA,DEC</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>spherical coordinates (radians)</TD> +</TR> +</TABLE></DL> +<P> <DL> +<DT><STRONG>RETURNED:</STRONG> +<DD> +<BR> +<TABLE CELLPADDING=3> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>RAZ1,DECZ1</EM></TD> +<TH ALIGN="LEFT"><B>D</B></TH> +<TD ALIGN="LEFT" NOWRAP>spherical coordinates of tangent point, +solution 1</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>RAZ2,DECZ2</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>spherical coordinates of tangent point, +solution 2</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>N</EM></TD> +<TD ALIGN="LEFT"><B>I</B></TD> +<TD ALIGN="LEFT" NOWRAP>number of solutions:</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> 0 = no solutions returned (note 2)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> 1 = only the first solution is useful (note 3)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> 2 = there are two useful solutions (note 3)</TD> +</TR> +</TABLE></DL> +<P> <DL> +<DT><STRONG>NOTES:</STRONG> +<DD><DL COMPACT> +<DT>1. +<DD>The RAZ1 and RAZ2 values returned are in the range <IMG WIDTH="43" HEIGHT="25" ALIGN="MIDDLE" BORDER="0" + SRC="img66.gif" + ALT="$0\!-\!2\pi$">.<DT>2. +<DD>Cases where there is no solution can only arise near the poles. +For example, it is clearly impossible for a star at the pole + itself to have a non-zero <IMG WIDTH="10" HEIGHT="27" ALIGN="MIDDLE" BORDER="0" + SRC="img92.gif" + ALT="$\xi$"> value, and hence it is + meaningless to ask where the tangent point would have to be + to bring about this combination of <IMG WIDTH="10" HEIGHT="27" ALIGN="MIDDLE" BORDER="0" + SRC="img92.gif" + ALT="$\xi$"> and <IMG WIDTH="10" HEIGHT="13" ALIGN="BOTTOM" BORDER="0" + SRC="img23.gif" + ALT="$\delta$">. <DT>3. +<DD>Also near the poles, cases can arise where there are two useful + solutions. The argument N indicates whether the second of the + two solutions returned is useful. N=1 + indicates only one useful solution, the usual case; under + these circumstances, the second solution corresponds to the + ``over-the-pole'' case, and this is reflected in the values + of RAZ2 and DECZ2 which are returned. + <DT>4. +<DD>The DECZ1 and DECZ2 values returned are in the range <IMG WIDTH="25" HEIGHT="25" ALIGN="MIDDLE" BORDER="0" + SRC="img47.gif" + ALT="$\pm \pi$">, but in the ordinary, non-pole-crossing, case, the range is + <IMG WIDTH="41" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img15.gif" + ALT="$\pm\pi/2$">. <DT>5. +<DD>RA, DEC, RAZ1, DECZ1, RAZ2, DECZ2 are all in radians. + <DT>6. +<DD>The projection is called the <I>gnomonic</I> projection; the + Cartesian coordinates <IMG WIDTH="41" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img85.gif" + ALT="$[\,\xi,\eta\,]$"> are called + <I>standard coordinates.</I> The latter + are in units of the distance from the tangent plane to the projection + point, <I>i.e.</I> radians near the origin. + <DT>7. +<DD>When working in <IMG WIDTH="58" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img50.gif" + ALT="$[\,x,y,z\,]$"> rather than spherical coordinates, the + equivalent Cartesian routine sla_DTPV2C is available. + </DL></DL> +<BR> <HR> +<A NAME="tex2html1206" HREF="node79.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html1204" HREF="node13.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html1198" HREF="node77.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="tex2html1207" HREF="node79.html">SLA_DTPV2C - Plate centre from and x,y,z</A> +<BR> +<B>Up:</B> <A NAME="tex2html1205" HREF="node13.html">SUBPROGRAM SPECIFICATIONS</A> +<BR> +<B> Previous:</B> <A NAME="tex2html1199" HREF="node77.html">SLA_DTP2V - Tangent Plane to Direction Cosines</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> |