11: Photographic Astrometry — Read

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Astrometry is the art and science of measuring positions of celestial objects, and indeed the first step in determining the orbit of a new asteroid or comet is to obtain a set of good astrometric positions. For much of the twentieth century, most astrometric positions were determined photographically.

11.1: Introduction to Photographic Astrometry
Why, then, would you ever want to read a chapter on photographic astrometry? Well, perhaps you won’t. After all, to convert your observations to right ascension and declination today, a single key on your computer keyboard will do it all. But this is because someone, somewhere, and usually a very anonymous person, has written for you a highly efficient computer program that carries out all the necessary calculations. Thus you can probably safely bypass this chapter.
11.2: Standard Coordinates and Plate Constants
This page explains the relationship between equatorial coordinates of stars and their projections on a tangent plane as viewed through a telescope. It covers standard coordinates, spherical triangles, and deriving calculations from equatorial coordinates, while addressing practical measurement challenges.
11.3: Refinements and Corrections
This page covers essential refinements for accurate astronomical work, emphasizing parallax, proper motion, refraction, and optical distortions. It stresses the necessity of accounting for measurement errors, catalogue inaccuracies, and human or instrumental faults. The text points out that users of custom reduction programs understand these refinements, while users of pre-packaged software might not be aware of the corrections made.

Thumbnail: Motion of barycenter of solar system relative to the Sun. Carl Smith derivative work: Rubik-wuerfel

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