The hydrogen line alpha (H-alpha) is the dominant emission line of the night sky in the visible spectrum. Almost all objects contain emissions of this spectral component in bright red. With sensitive sensors, amazing images can be achieved after a short time.
The Altair Astro 3nm ULTRA filters are designed for astro imaging of nebulae with Mono CCD or CMOS cameras, blocking light pollution by cutting out the light pollution wavelengths. The filter blocks UV IR and has an anti-reflection AR coating to suppress halos around bright stars.