Electronographic Camera

Electronographic Camera 

an electron-optical instrument for the reproduction of images of objects on an electrono-graphic plate that is sensitive to the action of a flow of electrons. In astronomy the electronographic camera is used in conjunction with telescopes of low relative aperture in such a way that the optical image of an object is projected onto the photocathode of the camera. The photoelectron flow that arises is projected by means of some electron-optical system (electrostatic, magnetic, electromagnetic, or combined system) onto an electronographic plate, where the electron image of the object corresponding to the optical image on the photocathode is fixed. The more efficient use of the luminous flux available (in comparison with conventional photography), especially in the infrared region of the spectrum, makes it possible to reduce photographic exposure times significantly and, in many cases, to increase the limiting magnitude of the telescope.

Since the density of an image on an emulsion is proportional to the density of the incident electron flow, and the latter thus depends on the illuminance on the photocathode, the characteristic curve of an electronographic camera does not exhibit the underexposure region that is typical of conventional photographic emulsions. This feature, together with the significant capacity of electronographic emulsions to register the total accumulated action of electrons over a period of time and the high resolution of such emulsions, makes it possible to use electronographic cameras to detect faint details of the spectra and structure of diffuse celestial objects.

The first astronomical electronographic camera was designed by A. Lallemand of France in the 1950’s.

REFERENCE

Kurs astrofiziki i zvezdnoi astronomii, 3rd ed., vol. 1. Edited by A. A. Mikhailov. Moscow, 1973.

N. P. ERPYLEV