General astronomy

General astronomy

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General astronomy

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 ...

A slow but relatively uniform motion of the earth's rotational axis that causes changes in the coordinate systems used for mapping the sky. The earth's axis of rotation does not always point in the ...

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.

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.

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 ...

Magnitude

Astronomy; General astronomy

The units used to describe brightness of astronomical objects. The smaller the numerical value, the brighter the object. The human eye can detect stars to 6th or 7th magnitude on a dark, clear night ...

orbital elements

Astronomy; General astronomy

Parameters (numbers) that determine an object's location and motion in its orbit about another object. In the case of solar-system objects such as comets and planets, one must ultimately account for ...