Askar Colour Magic SII narrowband filter 3 nm 2 inch for night photography

Sulfur gives little light in most nebulae, and precisely because of this it falls away into the sky glow without a filter. The Askar SII filter of 3 nm only lets through a narrow band around the SII line of sulfur, in deep red. Almost all other light is blocked, including that from streetlights and the moon.

The 2 inch filter is intended for a monochrome camera, like the ones you find at astronomical cameras for deep-sky. In the well-known Hubble palette, SII is combined with the H-alpha filter of 3 nm and an OIII filter is used to build color images of nebulae.

Because the signal from sulfur is weaker than that from hydrogen, you will need a longer total exposure time. Plan therefore for more nights of SII than of H-alpha observations. If you use a very bright telescope, then check whether a 3 nm filter is suitable for that purpose. The filter is for the night sky, not for the sun.

All three filters can be found in the Colour Magic set of three.