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The Astronomik UHC filter (there are two--I'm describing the narrower one) has about 10nm wider a bandwidth than the Lumicon UHC and about 13nm wider bandwidth than the DGM.
I don't think that's necessarily a problem.
I disagree with David Knisely on this one. He has often said there is value in having multiple Broadband filters, but that one should always pick the UHC and/or O-III filter that produces the highest contrast on the nebulae.
I think there is value in having multiple choices for different purposes.
For instance, a wider filter would show more stars (an observer might like that) and only sacrifice a bit of contrast on the nebula. And a wider filter would be usable at a higher power without dimming the overall field image excessively. That reduced dimming could be important in a small aperture, even at low powers. A wider filter might do fine in a larger aperture when the view is already great and you just want to turn up the contrast.
I use two different O-III filters a lot: the Lumicon (12nm bandwidth) and the TeleVue (23nm bandwidth), and for all those reasons.
What advice do you give to someone who can afford only one filter? That's the important question. I think I'd start out with a filter that runs fairly narrow in its category, has a high transmission, yet doesn't clip any of the desirable wavelengths during transmission.
The wider filter doesn't make the nebula invisible though, and your telescope won't break if you use one. I think if one chooses a filter knowing what the filter is, what it does, and how it differs from its competitors, there is nothing wrong with the choice.
But since nebula filters are fairly expensive, going into the choice blind, without knowing what one is choosing, might result in results that are less than might be delivered with another filter.
I do wish the manufacturers spent more time giving us specifications like bandwidth and transmission percentage averages at the important wavelengths instead of idealized transmission curves.
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