wcsndmap docstring
@@ -602,8 +602,10 @@ class WcsNDMap(WcsMap):
"""Convolve map with a kernel.
If the kernel is two dimensional, it is applied to all image planes likewise.
- If the kernel is higher dimensional it must match the map in the number of
- dimensions and the corresponding kernel is selected for every image plane.
+ If the kernel is higher dimensional should either match the map in the number of
+ dimensions or the map must be an image (no non-spatial axes). In that case, the
+ corresponding kernel is selected and applied to every image plane or to the single
+ input image respectively.
Parameters
----------
