Astronomical Negative

a photograph of the stellar sky (negative) obtained with the use of an astrograph or other telescope for determining the spherical coordinates of celestial bodies, their proper motions, parallaxes, brightnesses, light indices, and other characteristics; and also for determining the orbits of binary stars. Astronomical negatives used in determining the parallaxes of stars and orbits of binary stars are obtained with the aid of long-focus astrographs (with focal lengths up to 19 m), which provides more accurate results. Astronomical negatives with images of artificial earth satellites, taken with satellite cameras, are used for precise studies of the motion of satellites and for solving some practical problems, particularly problems in satellite geodesy. Special types of high-sensitivity photographic plates and films are used for astronomical negatives.

Many astronomical observatories have “plate libraries,” which contain thousands of astronomical negatives obtained over the course of many decades and which serve as valuable material for research into slowly evolving cosmic phenomena.