Designed exclusively for deep-sky imaging of emission nebulas with CCD cameras, this high-performance filter transmits 90 percent of light at the hydrogen-alpha line of 656.3nm and has a very narrow full width at half-maximum (FWHM) bandpass of 7nm. It blocks out all other light, including artificial light pollution and moonlight. It also blocks infrared (IR) light. The result is a dramatic boost in contrast, revealing subtle nebular details that are usually washed out by contrast-killing broadband light. Stars come out tight and sharp.