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.