#10 Use Astroquery as backup

kungpao/extinction.py

@@ -20,12 +20,20 @@ def radec_extinction(ra, dec, a_lambda=1.0):
             Convert the e_bv value into extinction in magnitude unit.
 
     """
+    coords = SkyCoord(ra, dec, frame='icrs', unit='deg')
+
     try:
+        # mwdust by Jo Bovy
         import mwdust
         sfd = mwdust.SFD(sf10=True)
-        coords = SkyCoord(ra, dec, frame='icrs', unit='deg')
         ebv = sfd(coords.galactic.l.deg, coords.galactic.b.deg, 0)
     except ImportError:
-        raise Exception("# Both mwdust and sncosmo are not available")
+        try:
+            # Try querying the IRSA dust map instead
+            from astroquery.irsa_dust import IrsaDust
+            extinction_tab = IrsaDust.get_extinction_table(coords)
+            ebv = (extinction_tab['A_SFD'] / extinction_tab['A_over_E_B_V_SFD'])[1]
+        except ImportError:
+            raise Exception("# Need mwdust by Jo Bovy or Astroquery")
 
     return a_lambda * ebv