Index: /trunk/Ohana/src/opihi/cmd.astro/altaz.c
===================================================================
--- /trunk/Ohana/src/opihi/cmd.astro/altaz.c	(revision 17282)
+++ /trunk/Ohana/src/opihi/cmd.astro/altaz.c	(revision 17282)
@@ -0,0 +1,88 @@
+# include "astro.h"
+
+# define dCOS(A)   ((double) cos ((double)RAD_DEG*A))
+# define dSIN(A)   ((double) sin ((double)RAD_DEG*A))
+
+double atan2 (double y, double x);
+
+int altaz (int argc, char **argv) {
+  
+  double alt, az, lat, rot;
+  double ha, dec;
+  double sind, sinh, cosh;
+  char *latstr;
+
+  if (argc != 6) goto usage;
+
+  if (!strcmp (argv[1], "-h")) goto radec;
+  if (!strcmp (argv[1], "-c")) goto altaz;
+
+ radec:
+  /* ha/dec -> alt/az */
+  ha  = atof (argv[2]);
+  dec = atof (argv[3]);
+
+  latstr = get_variable ("LATITUDE");
+  if (latstr == (char *) NULL) {
+    gprint (GP_ERR, "please define $LATITUDE\n");
+    return (FALSE);
+  }
+  lat = atof (latstr);
+  free (latstr);
+ 
+  sind = dSIN (dec) * dSIN (lat) + dCOS (dec) * dCOS (ha) * dCOS (lat);
+  alt  = DEG_RAD * asin (sind);
+
+  sinh = - dCOS (dec) * dSIN (ha);
+  cosh =   dSIN (dec) * dCOS (lat) - dCOS (dec) * dCOS (ha) * dSIN (lat);
+
+  az = DEG_RAD * atan2 (sinh, cosh);
+  set_variable (argv[4], alt);
+  set_variable (argv[5], az);
+
+  sinh = -dCOS(az) * dSIN(alt) * dSIN(ha) * dSIN(lat) + dSIN(az) * dSIN(alt) * dCOS(ha) - dSIN(ha) * dCOS(alt) * dCOS(lat);
+  cosh = -dSIN(az) * dSIN(ha) * dSIN(lat) - dCOS(az) * dCOS(ha);
+  rot = -DEG_RAD * atan2 (sinh, cosh);
+  set_variable ("ROT", rot);
+
+  return (TRUE);
+  
+ altaz:
+  /* alt/az -> ha/dec */
+  alt = atof (argv[4]);
+  az  = atof (argv[5]);
+
+  latstr = get_variable ("LATITUDE");
+  if (latstr == (char *) NULL) {
+    gprint (GP_ERR, "please define $LATITUDE\n");
+    return (FALSE);
+  }
+  lat = atof (latstr);
+  free (latstr);
+
+  sind = dSIN (alt) * dSIN (lat) + dCOS (alt) * dCOS (az) * dCOS (lat);
+  dec  = DEG_RAD * asin (sind);
+
+  sinh = -dCOS (alt) * dSIN (az);
+  cosh =  dSIN (alt) * dCOS (lat) - dCOS (alt) * dCOS (az) * dSIN (lat);
+
+  ha = DEG_RAD * atan2 (sinh, cosh);
+  set_variable (argv[2], ha);
+  set_variable (argv[3], dec);
+
+  sinh = -dCOS(az) * dSIN(alt) * dSIN(ha) * dSIN(lat) + dSIN(az) * dSIN(alt) * dCOS(ha) - dSIN(ha) * dCOS(alt) * dCOS(lat);
+  cosh = -dSIN(az) * dSIN(ha) * dSIN(lat) - dCOS(az) * dCOS(ha);
+  rot = -DEG_RAD * atan2 (sinh, cosh);
+  set_variable ("ROT", rot);
+
+  return (TRUE);
+  
+ usage:
+  gprint (GP_ERR, "USAGE: altaz -h (ha) (dec) (alt) (az)\n");
+  gprint (GP_ERR, "USAGE: altaz -c (ha) (dec) (alt) (az)\n");
+  gprint (GP_ERR, "       -h alt/az to ha/dec, -c ha/dec to alt/az\n");
+  gprint (GP_ERR, "       returned values in variables provided\n");
+  return (FALSE);
+
+}
+