6 Terms
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General astronomy
Industry: Astronomy
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General astronomy
right ascension
Astronomy; General astronomy
One element of the astronomical coordinate system on the sky, which can be though of as longitude on the earth projected onto the sky. Right ascension is usually denoted by the lower-case Greek ...
perigee
Astronomy; General astronomy
The point where (and when) an object's orbit about the earth in which it is closest to the earth; only applicable to objects orbiting the earth (not to objects orbiting the sun --- a common error).
perihelion
Astronomy; General astronomy
The point where (and when) an object orbiting the sun is closest to the sun.
perturbations
Astronomy; General astronomy
Gravitational influences ("tugging" and "pulling") of one astronomical body on another. Comets are strongly perturbed by the gravitational forces of the major planets, particularly by the largest ...
phase angle
Astronomy; General astronomy
For a solar system object besides the earth and sun, the angle between the earth and the sun (or the earth's elongation from the sun) as seen from that third object. The phase angle is given in ...
refractor
Astronomy; General astronomy
A telescope that uses as its primary optical element a lens. Binoculars are a type of refractor. In general, refractors are much more expensive to build and buy than are reflectors.
reflector
Astronomy; General astronomy
A telescope that uses as its primary optical element a mirror. Nearly all large telescopes in use today by amateur and professional astronomers are reflecting telescopes.
