The precision calcium photometer: A New Instrument for Astroseismology

The Precision CAlcium Photometer (PCAP) has been built with characteristics optimized for amplitude astroseismology. The instrument consists of two units: an on-telescope optical system that forms and stabilizes a stellar image onto a 200 micron optical fiber; and a spectrometer unit that accepts the light from the fiber and integrates the Calcium II H and K lines (3968.5 Å and 3933.7 Å), along with adjacent continuum regions, in a photon-counting mode. Some key system characteristics include active image stabilization, a 12-meter optical fiber with ~70% transmission at 3950 Å, and a thermally and mechanically stable spectrometer. A description of the instrument and of laboratory and on-telescope test runs are discussed below.