fixed skycenter declination bug

toolbox.py

@@ -187,16 +187,21 @@ def get_binning(header, obsparam):
 
 def skycenter(catalogs, ra_key='ra.deg', dec_key='dec.deg'):
     """derive center position and radius from catalogs"""
-
+    from astropy.coordinates import SkyCoord
+    from astropy import units as u
+
     min_ra  = min([numpy.min(cat[ra_key]) for cat in catalogs])
     max_ra  = max([numpy.max(cat[ra_key]) for cat in catalogs])
     min_dec = min([numpy.min(cat[dec_key]) for cat in catalogs])
     max_dec = max([numpy.max(cat[dec_key]) for cat in catalogs])
+
+    ra, dec = (max_ra+min_ra)/2, (max_dec+min_dec)/2
 
-    ra, dec = old_div((max_ra+min_ra),2.), old_div((max_dec+min_dec),2.)
-    rad     = numpy.sqrt((old_div((max_ra-min_ra),2.))**2 + 
-                         (old_div((max_dec-min_dec),2.))**2)
+    lower_left= SkyCoord(ra=min_ra, dec=min_dec, frame='icrs', unit='deg')
+    upper_right = SkyCoord(ra=max_ra, dec=max_dec, frame='icrs', unit='deg')
 
+    rad     = lower_left.separation(upper_right).deg/2
+
     return ra, dec, rad