Changeset 30658

Timestamp:

Feb 16, 2011, 4:14:16 PM (15 years ago)

Author:

eugene

Message:

update galactic coords to FK5

File:

• trunk/Ohana/src/opihi/cmd.astro/coord_systems.c (modified) (2 diffs)

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

@@ -21 +21 @@
           break;
         case COORD_GALACTIC:
-          transform->phi = -62.60*RAD_DEG;
-          transform->Xo  = 282.25*RAD_DEG;
-          transform->xo  =  33.00;
+
+          // J2000 FK5 transformation from Liu et al 2011 (A&A 526, A16)
+          transform->phi = -62.8717488056*RAD_DEG;
+          transform->Xo  = 282.8594812080*RAD_DEG;
+          transform->xo  =  32.9319185700;
+
+          // these are derived from their eqn (10):
+          // \alpha^p_J =  12h 51m 26.27549s
+          // \delta^p_J = +27d 07' 41.7043"
+          // \theta_J   = 122.93191857 deg
+          // phi = -90 - \alpha^p_J
+          // Xo  = +90 - \delta^p_J
+          // xo  = \theta_J - 90
+
+          // Liu et al also propose an alternative ICRS definition using:
+          // \alpha^p_J =  12h 51m 26.27469s
+          // \delta^p_J = +27d 07' 41.7087"
+          // \theta_J   = 122.93192526 deg
+          // these differ from the above at the several milliarcsec level
+
+
+          // These values were used in the past, but transform to/from B1950.0
+          // transform->phi = -62.60*RAD_DEG;
+          // transform->Xo  = 282.25*RAD_DEG;
+          // transform->xo  =  33.00;
+
           break;
         case COORD_ECLIPTIC:
@@ -63 +86 @@
       switch (output) {
         case COORD_CELESTIAL:
-          transform->phi =  62.60*RAD_DEG;
-          transform->Xo  =  33.00*RAD_DEG;
-          transform->xo  = 282.25;
+          // J2000 transformation from Liu et al 2011 ()
+          transform->phi =  62.8717488056*RAD_DEG;
+          transform->Xo  =  32.9319185700*RAD_DEG;
+          transform->xo  = 282.8594812080;
+
+          // These values were used in the past, but transform to/from B1950.0
+          // transform->phi =  62.60*RAD_DEG;
+          // transform->Xo  =  33.00*RAD_DEG;
+          // transform->xo  = 282.25;
           break;
         case COORD_GALACTIC: