H-Alpha, O-III, S-II, H-Beta Narrowband Nebular Filter for Astrophotography

By using nebula filters, a significant increase in contrast can be achieved and you can expose longer until the the background is lightened up through stray light.
Nebula filters let pass certain parts of light where deep-sky objects emit. On the other hand, the unwanted stray light of the cities is suppressed. That allows longer exposure times. You can record fainter objects and gain more information. Nebula filers can be used with DSLR and CCD cameras.

On this page, you can find:
narrowband nebula filters for strong increase in contrast and longer exposure times
filters for specific emission ranges like H-alpha, H-beta, O-II, S-II, for extreme gain in contrast and for false colour images