The Reticon Spectrophotometer at Cima Ekar Observatory

Abstract

A spectrophotometer employing linear arrays of Reticon photodiodes has been used at Asiago observatory since August 1977. The first version, with a 128 - element array, has already been described in detail (Barbieri et al. 1978). The final configuration has 512 photodiodes, each 50.8 μm high, so that 2-5 cm of spectrum can be recorded in a single exposure. The spectrophotometer is mounted at the focal plane of the Boiler & Chivens spectrograph of the 182 cm telescope; with the 600 groves/mm grating the diode width corresponds to 5.9 Å. Two other gratings are available, respectively with 400 and 7200 grooves/mm. A fairly sophisticated computer system permits a remarkable flexibility of operation, with real time display on the CRT of the acquired data and recording on mag. tape. To subtract the thermal current and the sky, the star is taken out of the slit by tilting a transparent plate in front of the spectrograph, always under computer control; the astronomer can choose different star/sky exposure times so as to optimize the observing procedure. Guiding can be performed from the control cabinet with an integrating SEC-TV system.