fixes #160
Highlights the need for a better NGC/M catalog (which is easier to import) or at least a better import of the one we have.
e.g.: NGC 650 and 651 are part of M76, but this can't be seen in our catalog view.
What changed:
adding a set in setup.py to not add the same messier twice
adding checks on CatalogBase to avoid having duplicate sequences added
fixes #160 Highlights the need for a better NGC/M catalog (which is easier to import) or at least a better import of the one we have. e.g.: NGC 650 and 651 are part of M76, but this can't be seen in our catalog view.
What changed: