Nebula Filter S-II 2-inch 12nm

Street lights brighten the sky over every town, and in an image that glow lands on the sensor along with the nebula. The Explore Scientific S-II filter passes only the emission line of ionized sulfur at 672 nm, in a 12 nm passband, and absorbs almost all artificial light, so the sulfur emission of emission nebulae, planetary nebulae and supernova remnants records even under a brightened sky.

Key Features

• For the camera, not the eyepiece. Ionized sulfur glows at 672 nm, in the deep red, where the dark-adapted eye is about 1/8,000 as sensitive as at its peak. Through an eyepiece this filter shows little or nothing. With a camera it is the sulfur channel of narrowband imaging.
• Ionized sulfur line at 672 nm. Passes the S-II emission line and absorbs the other emission lines.
• 12 nm passband.
• Absorbs almost all artificial light.
• 2-inch size, for 2-inch filter holders and imaging trains.
• Individual test report. Each filter ships with its own test sheet, carrying its serial number and measured transmission curve.

Ideal For

• Narrowband imagers building a sulfur, hydrogen-alpha and oxygen set. The Nebula Filter H-Alpha 2-inch 12nm is the matching hydrogen-alpha filter in this size and passband.
• Imagers under suburban skies, where the narrow passband keeps most of the sky glow off the sensor.
• Smaller imaging trains: the same filter comes in the 1.25-inch size as the Nebula Filter S-II 1.25-inch 12nm.