Chromospheric helium imaging photometer (an instrument for high time cadence 1083-nm wavelength solar observations)

The scientific motivation, design criteria, and specifications for a new ground-based instrument to observe the Sun in the He I 1083-nm spectral line is described. The instrument employs a liquid-crystal tunable Lyot-type spectral filter and an array detector that allows the full solar disk to be observed with a time cadence of minutes. We describe the telescope's optical and mechanical features and discuss computer interface and data-reduction procedures employed. Instrument performance during the initial year of operation of the telescope at its high-altitude site is summarized. (C) 1998 Optical Society of America.