Changeset 7964

Timestamp:

Jul 24, 2006, 3:17:36 PM (20 years ago)

Author:

eugene

Message:

added LST function

Location:

trunk/Ohana/src

Files:

• libohana/include/ohana.h (modified) (1 diff)
• libohana/src/time.c (modified) (1 diff)
• opihi/cmd.astro/Makefile (modified) (1 diff)
• opihi/cmd.astro/getlst.c (added)
• opihi/cmd.astro/init.c (modified) (2 diffs)

trunk/Ohana/src/libohana/include/ohana.h

@@ -156 +156 @@
 double  sec_to_mjd             PROTO((time_t second));
 time_t  mjd_to_sec             PROTO((double mjd));
+double  ohana_lst              PROTO((double jd, double longitude));
 
 int     hstgsc_hms_to_deg      PROTO((double *h0, double *h1, double *d0, double *d1, char *string));

trunk/Ohana/src/libohana/src/time.c

@@ -395 +395 @@
  * 99:02:15:12h23m30s
  */
+
+
+/* returns the local MEAN sidereal time (dec hrs) at julian date jd
+   at west longitude long (decimal hours).  Follows
+   definitions in 1992 Astronomical Almanac, pp. B7 and L2.
+   Expression for GMST at 0h ut referenced to Aoki et al, A&A 105,
+   p.359, 1982.  On workstations, accuracy (numerical only!)
+   is about a millisecond in the 1990s.
+   EAM: function from skycalc (thorstensen) 
+*/
+#define  J2000             2451545.        /* Julian date at standard epoch */
+#define  SEC_IN_DAY        86400.
+
+double ohana_lst (double jd, double longitude) {
+
+  double t, ut, jdmid, jdint, jdfrac, sid_g, sid;
+  long sid_int;
+
+  jdint = (int) jd;
+  jdfrac = jd - jdint;
+
+  if (jdfrac < 0.5) {
+    jdmid = jdint - 0.5;
+    ut = jdfrac + 0.5;
+  } else {
+    jdmid = jdint + 0.5;
+    ut = jdfrac - 0.5;
+  }
+
+  t = (jdmid - J2000)/36525;
+  sid_g = (24110.54841+8640184.812866*t+0.093104*t*t-6.2e-6*t*t*t)/SEC_IN_DAY;
+  sid_int = sid_g;
+  sid_g = sid_g - (double) sid_int;
+  sid_g = sid_g + 1.0027379093 * ut - longitude/24.;
+  sid_int = sid_g;
+  sid_g = (sid_g - (double) sid_int) * 24.;
+  if (sid_g < 0.) sid_g = sid_g + 24.;
+  return (sid_g);
+}

trunk/Ohana/src/opihi/cmd.astro/Makefile

@@ -33 +33 @@
 $(SDIR)/gauss.$(ARCH).o            \
 $(SDIR)/getvel.$(ARCH).o           \
+$(SDIR)/getlst.$(ARCH).o           \
 $(SDIR)/medianmap.$(ARCH).o        \
 $(SDIR)/mkgauss.$(ARCH).o          \

trunk/Ohana/src/opihi/cmd.astro/init.c

@@ -15 +15 @@
 int gaussfit                PROTO((int, char **));
 int getvel                  PROTO((int, char **));
+int getlst                  PROTO((int, char **));
 int imfit                   PROTO((int, char **));
 int imsub                   PROTO((int, char **));
@@ -48 +49 @@
   {"gauss",       gauss,        "get statistics on a star, assuming gaussian profile"},
   {"getvel",      getvel,       "rotcurve to velocities"},
+  {"getlst",      getlst,       "return LST given time and longitude"},
   {"imfit",       imfit,        "fit function"},
   {"imsub",       imsub,        "subtract function"},