[PChis (Paul)]

Hi All,
I acquired this filter with some gear I purchased. It is possibly 20 years of age and in excellent condition. Following are the specs which are written on the case.

Hydrogen-Beta 486nm 96.9%
Oxygen III 496nm 96.6%
Oxygen III 501nm 97.7%
Hydrogen-Alpha 656nm 91.8%

I have been using it in conjunction with a DSLR & 880mm refractor in a Bortle class 5 sky to reduce the effects of light pollution. My lights are taken at ISO100 and I seem to need 6+ minute exposures.
So the question is "is this an appropriate filter for this purpose?"
And should I be using something else?

Happy to field all feedback & comments.
Thanks.