The IDAS HEUIB-II-EOS (H-alpha Enhanced UV IRBlocking) filter is designed for enhanced spectrum Canon APS-C frame cameras
Besides removing the IR and UV ends of the spectrum which are often out of focus in refractive optics, it isolates the common H-alpha line relative to the surrounding extreme red end of the spectrum, making it easy to bring out the faint H-alpha emission nebulosity of astronomical photos, yet retain the background color balance of broadband photos.
The HEUIB-II filter also returns normal daylight color balance to spectrum-enhanced cameras as can be seen in this photo at right taken with normal DSLR auto-white-balance (AWB) enabled.
