KevinN So I guess you're saying that these fall under that "don't buy" category.
I wouldn't touch ZWO glass with a ten foot pole.
You should at least be able to tell the wide band filters from the narrowband filters, since they have significant overlap. I.e., green stacked with blue will still pass a lot of cyan light. That leaves the narrow band ones.
The difficulty is to tell H-beta from Oxygen-III (both pass cyan, but don't overlap), and sulphur from H-alpha (both pass deep red, and again don't overlap). You would need a friend with an H-beta and a H-alpha -- I think that is all you need.
Chen
