H band

Within astronomy, the term H band refers to an atmospheric window within the near-infrared range centered on 1.63 microns (1630 nm), i.e., 184 THz, and a photometric system passband aimed at this range, e.g., with a full width at half maximum of 350 nm. In addition to infrared-specific telescopes, many optical telescopes can observe in this range. The letter is also used to indicate the magnitude of the signal observed through the passband filter, e.g., citing "H = 1.5". The passband is incorporated into the 2MASS JHK photometric system, as well as other infrared photometric systems. Note that there is some variation in such bands, regarding the central wavelength and the FWHM, between different systems and surveys, but versions of the H band are generally designed to observe through the H atmospheric window.

The term H band also has other meanings outside astronomy, one being a radio communications band, which is nowhere near the above infrared band.