WCS/spectral_axis in Spectrum Object

[rh2082]

Describe the feature

It's confusing that you have to give a WCS and a spectral axis differently since they're both just ways of giving coordinates. This should be made clearer, either in the docs, or the API should detect whether spectral_axis is a WCS and handle it accordingly.

Proposed solution

No response

[samaloney]

Yea so the reason for this is the WCS/GWCS don't have any concept of bin edges, need to store the bin edges somewhere and that's on the spectral axis. So even if you have WCS which descpribe the spectral axis it won't have bin edges so need to also give the spectral axis. Now the code tries to check that if the WCS has a spectral axis it matches the one given.