General astronomy

General astronomy

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General astronomy

astrometry

Astronomy; General astronomy

The careful, precise measurement of astronomical objects, usually made with respect to standard catalogues of star positions. For comet orbit computations, astrometry good to 1" or 2" (1 or 2 arc ...

There are 60 minutes (denoted as 60') of arc in 1 degree. In the sky, with an unobstructed horizon (as on the ocean), one can see about 180 degrees of sky at once, and there are 90 degrees from the ...

aphelion

Astronomy; General astronomy

For an object orbiting the sun, the point (distance and time) where/when the object is furthest from the sun in its elliptical orbit.

altitude

Astronomy; General astronomy

The angular distance from the observer's horizon, usually taken to be that horizon that is unobstructed by natural or artificial features (such as mountains or buildings), measured directly up from ...

aperture

Astronomy; General astronomy

The size of the primary optical surface of an astronomical instrument (telescope), usually given in inches, centimeters, or meters. In the case of a reflecting telescope, the aperture usually refers ...

barycenter

Astronomy; General astronomy

The center of mass of a system of bodies, such as the solar system. When a comet, for example, is well outside the orbit of Neptune (the farthest major planet), it sees the sun and major planets ...

azimuth

Astronomy; General astronomy

Angular distance measured clockwise around the observer's horizon in units of degrees; astronomers usually take north to be 0 degrees, east to be 90 degrees, south to be 180 degrees, and west to be ...