TV Type Systems in Astronomy

The characteristics of an ideal optical instrument are examined, taking into account improvements required in conventional optical devices to increase instrument performance. New devices considered include solid state silicon photodiodes (vidicons), the image dissector scanner (IDS), and T.V. systems. In the analog T.V., photons hitting a photocathode produce electrons which are focussed onto a target. The target is a stable substrate which can store the accumulating charge patterns as it builds up for several hours if necessary, and, thus, acts as an analog storage device. The development of a useful digital T.V. depends on advances involving an enhancement of the gain.