T

Telescope:
(1) Technical instrument used to see distant objects as stars.
(2) Constellation of the southern hemisphere.

Telescope, catadioptric:
A telescope using a lens-mirror combination for compound objective.

Telescope, reflecting:
A telescope with a mirror objective

Telescope, refracting:
A telecope using a lens (usually achromatic) as an objective. (Learn more about telerscopes from Nick Strobels lecturenotes about telescopes.

Telescope mounting, altazimuth:
A mounting with two axes (one horizontal and one vertical, employing azimuth and altitude) to facilitate scanning in the horizn system.

Telescope mounting, equatorial:
One rotatable axis, set parallel to the earth's axis of rotation, compensates for diurnal motion of the heavenly bodies in right ascension. The other axis permits adjustment in declination.

Terminator:
The dividing line between the illuminated and shadowed portions of the lunar or planetary disk.

Time, Local Mean (LMT):
Solar time for a given location reduced from apparent to mean by application of the equation of time. Also called Local Solar Time.

Time, Standard Mean (SMT)
Mean solar time for some standard adopted longitude (for example, Eastern Standard Time, Central European Time, Mountain or Pacific Standard Times; see: scholar pages about time).

Transit:
When a small celestial body moves in front of a much larger one (as when Mercury or Venus appears in silhouette against the solar disk or when a satellite passes in front of Jupiter or Saturn), the event is termed transit rather than eclipse. The shadow of a satellite may also transit the disk of its primary.