Nebula Bandpass Filters are designed to bring out the nebulosity in deep sky objects by passing those exact bandwiths that show the nebulosity and partially blocking part of the other wavelengths. The UHC filter is the broadest, allowing the Hα bands and the OIII bands. This makes it the best general purpose Nebula filter. The OIII is narrower in bandwidth, passing just the OIII bands. It is best for objects heavy in OIII emissions, like the Veil Nebula. The Hydrogen-β Filter passes just the Hydrogen-β band. This aids the viewing of extremely faint nebulous objects such as the Horsehead, Cocoon and California Nebulae.