1. A particle of light that acts as an individual unit of energy.
2. A quantum of electromagnetic energy that can be considered as a particle with no mass, no charge, and traveling at the speed of light.

As "packets" of light they can be individually counted and used to build up a picture of; for example, a distant galaxy.

An electronic detector system that has contributed to the knowledge of astronomy.

This detector is a four-stage, magnetically-focused image intensifier, coupled via a lens to a plumbicon television camera tube.

A plumbicon is the development of the vidicon television camera tube in which the photosensitive material is lead oxide.

A plumbicon is a registered trademark of Philips for its Lead Oxide (PbO) target vidicons or camera tubes in which a charge-density patterns are formed by photoconduction and stored on photoconductor surfaces that are scanned by electron beams; usually, of low-velocity electrons; used chiefly in industrial television cameras.