Added check on rotation units for FieldofView

pywwt/annotation.py

@@ -263,6 +263,15 @@ class FieldOfView():
     # a more efficient method than CircleCollection of changing trait values?
     
     def __init__(self, parent, telescope, center, rot, **kwargs):
+        # make sure rot is astropy quantity in proper units for self._rotate()
+        try:
+            if not rot.unit.is_equivalent(u.deg):
+                raise AttributeError
+        except AttributeError:
+            raise ValueError('rotate argument must be Astropy quantity with '
+                             'degree or radian-equivalent units')
+
+        # get the JSON list of FOVs from parent BaseWWTWidget class
         self.parent = parent
         self._available = self.parent.instruments.available
         self._entry = self.parent.instruments.entry
@@ -274,7 +283,8 @@ class FieldOfView():
     def _gen_fov(self, telescope, center, rot, **kwargs):
         # test if telescope is available
         if telescope not in self._available:
-            raise ValueError('the given telescope\'s field of view is unavailable at this time')
+            raise ValueError('the given telescope\'s field of view is '
+                             'unavailable at this time')
 
         position = self._entry[telescope][0]
         dimensions = self._entry[telescope][-1]
@@ -282,39 +292,43 @@ class FieldOfView():
 
         # test that pos matches what the user entered
         if center and position == 'absolute':
-            raise ValueError('the given telescope does not take center coordinates')
+            raise ValueError('the given telescope does not take center '
+                             'coordinates')
         elif not center and position == 'relative':
             raise ValueError('the given telescope requires center coordinates')
 
         for panel in dimensions:
             ras = (panel[0] * u.deg).value
             decs = (panel[1] * u.deg).value
-            ra_r, dec_r = self._rotate(ras, decs, rot)
 
-            if position == 'absolute':
-                ra_tr, dec_tr = ra_r, dec_r
-            else:
+            # rotate points if necessary
+            if position == 'relative' and rot != 0:
+                ras, decs = self._rotate(ras, decs, rot)
+                
+            # translate points to user-specified location if relative
+            if position == 'relative':
                 center_ra = center.ra.to(u.deg).value
                 center_dec = center.dec.to(u.deg).value
-                
-                dec_tr = center_dec + dec_r
+
+                decs = center_dec + decs
                 # scale RA by dec (due to polar contraction of spherical coords)
-                ra_tr = center_ra + ra_r / np.cos(dec_tr * u.deg).value
+                ras = center_ra + ras / np.cos(decs * u.deg).value
 
                 # check that abs(dec) < 90. if not, adjust it, and then
                 # set the corresponding ra to be swapped by 180
-                for i, dec in enumerate(dec_tr):
+                for i, dec in enumerate(decs):
                     if abs(dec) > 90:
                         if dec < -90:
-                            dec_tr[i] = -90. - (dec + 90.)
+                            decs[i] = -90. - (dec + 90.)
                         else: # dec > 90
-                            dec_tr[i] = 90. - (dec - 90.)
-                        ra_tr[i] += 180.
-            
-            corners = SkyCoord(ra_tr, dec_tr, unit=u.deg)
+                            decs[i] = 90. - (dec - 90.)
+                        ras[i] += 180.
+
+            corners = SkyCoord(ras, decs, unit=u.deg)
             if self.parent.galactic_mode:
                 corners = corners.galactic
 
+            # draw the panel
             annot = self.parent.add_polygon(corners, **kwargs)
             self.active.append(annot)
 
@@ -327,7 +341,7 @@ class FieldOfView():
 
     def remove(self):
         """
-        Removes the specified annotation from the current view.
+        Removes the specified field of view from the viewer.
         """
         for annot in self.active:
             annot.remove()