almucantar

Century Dictionary and Cyclopedia

1. n. In astronomy, a small circle of the sphere parallel to the horizon; a circle or parallel of altitude. When two stars are on the same almucantar they have the same altitude.
2. n. An astronomical instrument (invented by S. C. Chandler) consisting of a telescope provided with horizontal wires and mounted upon a box floating upon mercury. The float is first turned round so as to point the telescope east of the meridian, and the time of rising of a star over the wires is noted; the telescope is then pointed to west of the meridian, and the time of descending of a star is noted. In this way, if the positions of the stars are known, the correction of a timepiece and the latitude may be determined; on the other hand, if these are known, either the right ascensions or the declinations of the stars may be determined. The instrument is of great value on account of its having fewer instrumental errors than a meridian circle.

Wiktionary

1. n. archaic a small circle on the celestial sphere, parallel to the horizon, that is used in astronomy and navigation to show altitude of a star or any other heavenly body.

GNU Webster's 1913

1. n. (Astron.), Archaic A small circle of the sphere parallel to the horizon; a circle or parallel of altitude. Two stars which have the same almucantar have the same altitude. See almacantar.