band_pass: Spectral data for filters of different 'types'
Description
Names of datasets containing the wavelengths and tabulated values for
fractional spectral trabsmittance according to their type. Band-pass
filters transmit a range of wavelengths, but block shorter and longer
ones. Long-pass filters absorb wavelengths shorter than their cut-off and
short-pass filters absorb wavelengths longer than their cut-off.