Fix: correct ICRS camera orientation

tests/test_geodesic.c

@@ -45,6 +45,14 @@ int main(void) {
   result = result || check_ray(&source, &look_at_ra_zero,
                                (double[]){1.0, 0.0, 0.0},
                                (double[]){1.0, 0.0, 0.0});
+  /* Standard ICRS has +Z at the north celestial pole and +Y at increasing
+   * RA.  A right-handed north-up camera consequently has west to its right. */
+  result = result || check_ray(&source, &look_at_ra_zero,
+                               (double[]){0.0, 1.0, 0.0},
+                               (double[]){0.0, 0.0, 1.0}) ||
+           check_ray(&source, &look_at_ra_zero,
+                     (double[]){0.0, 0.0, 1.0},
+                     (double[]){0.0, -1.0, 0.0});
   ObserverTrack accelerated = {0};
   ObserverState final_observer;
   if (observer_track_generate_minkowski_acceleration(&accelerated, 1.52, 2.0,

tests/test_schwarzschild.c

@@ -22,12 +22,14 @@ int main(void) {
       observer_static_schwarzschild_ks_look_at(1.0, 40.0, 270.0, 30.0,
                                                 &oriented_observer) ||
       fabs(oriented_observer.coordinate_position[0]) > 1e-12 ||
-      fabs(oriented_observer.coordinate_position[1] + 20.0) > 1e-12 ||
-      fabs(oriented_observer.coordinate_position[2] - 20.0 * sqrt(3.0)) >
+      fabs(oriented_observer.coordinate_position[1] - 20.0 * sqrt(3.0)) >
+          1e-12 ||
+      fabs(oriented_observer.coordinate_position[2] + 20.0) >
           1e-12 ||
       fabs(oriented_observer.tetrad[1][1]) > 1e-12 ||
-      fabs(oriented_observer.tetrad[1][2] - 0.5 * sqrt(0.95)) > 1e-12 ||
-      fabs(oriented_observer.tetrad[1][3] + sqrt(0.95) * sqrt(3.0) / 2.0) >
+      fabs(oriented_observer.tetrad[1][2] + sqrt(0.95) * sqrt(3.0) / 2.0) >
+          1e-12 ||
+      fabs(oriented_observer.tetrad[1][3] - 0.5 * sqrt(0.95)) >
           1e-12 ||
       observer_inward_schwarzschild_ks(1.0, 30.0, 0.5,
                                        &inward_observer) ||