hpx map warning
@@ -8,6 +8,13 @@ classes. All HEALPix classes inherit from `~gammapy.maps.Map` which provides gen
interface methods that can be be used to access or update the contents of a map
without reference to its pixelization scheme.
+.. warning::
+
+ Gammapy uses `NEST` as default pixel order scheme, while `healpy`
+ functions have `RING` as the default (see https://healpy.readthedocs.io/en/1.11.0/index.html).
+ If you are interfacing Gammapy HEALPix maps with `healpy` functions, you need to specify the pixelization scheme
+ either while creating the Gammapy object or when using the `healpy` functions.
+
HEALPix geometry
----------------
