Changeset 24035

Timestamp:

May 1, 2009, 5:12:08 PM (17 years ago)

Author:

eugene

Message:

astrometry was allowing too high orders for the number of stars

File:

• trunk/psastro/src/psastroOneChipFit.c (modified) (1 diff)

trunk/psastro/src/psastroOneChipFit.c

@@ -64 +64 @@
         // modify the order to correspond to the actual number of matched stars:
         int Ndof_min = 3;
-        int order_max = 0.5*(3 + sqrt(4*match->n - 4*Ndof_min + 1));
+        int order_max = 0.5*(sqrt(4*match->n - 4*Ndof_min + 1) - 3);
         order = PS_MIN (order, order_max);
+
+        // order 0 : Ro -> nterms = 1 * 2;
+        // order 1 : Ro, Rx, Ry -> nterms = 3 * 2;
+        // order 2 : Ro, Rx, Ry, Rxx, Rxy, Ryy -> nterms = 6 * 2;
+        // order 3 : Ro, Rx, Ry, Rxx, Rxy, Ryy, Rxxx, Rxxy, Rxyy, Ryyy -> nterms = 10 * 2
+        // 2*(N+1)*(N+2)/2 = (N+1)*(N+2) = nterms;
+        // (order+1)(order+2) + ndof = nvalues
+        // order^2 + 3*order + 2 + ndof = nvalue;
+        // order^2 + 3*order + 2 + ndof - nvalue = 0;
+        // 2*order = -3 +/- sqrt (9 - 4*(2 - nvalue + ndof));
+        // 2*order = -3 +/- sqrt (9 - 8 + 4*nvalue - 4*ndof);
+        // 2*order = (sqrt (1 + 4*nvalue - 4*ndof) - 3);
 
         // if ((match->n < 11) && (order >= 3)) order = 2;