| 释义 |
almucantar|ælməˈkæntə(r)|
Forms: 4 almykantera, almicantera, 6 -ath, 7 almucanturie, almicantarath, 6–8 almicanter, 8 almicanther, 7–8 almucantar, 7–9 almacanter, -ar.
[a. Fr. almicantarat or almucantarat, also med.L. almi-, almucantarath; ad. Arab. almuqanṭarāt, pl. (with article) of muqanṭarah (cited by Golius in sense of ‘sundial’), deriv. of qanṭarah, a bridge, an arch.]
1. pl. Small circles of the sphere parallel to the horizon, cutting the meridian at equal distances; parallels of altitude. (The horizon itself was reckoned the first almucantar.) Also used in sing.
c1391Chaucer Astrol. ii. §5 The almykanteras in thin astrelabie ben compownet by two & two, where-as some Almykanteras in sondri Astrelabies ben compownet by on and on. 1594Davis Seamans Secr. ii. (1607) 8 Almicanters are circles of altitude..and are described upon the Zenith. 1594Blundevil Exerc. iii. i. xix. (ed. 7) 320 The first Almicanterath is the very oblique Horizon it selfe. a1625Fletcher Bloody Bro. iv. ii, Look upon the Astrolabe; you'll find it Four almucanturies at least. 1672Strode in Rigaud Corr. Sci. Men (1841) II. 441 The sun's almacanters delineated on an horizontal dial are hyperbolas, except when the sun is in the equator. 1768Smeaton in Phil. Trans. LVIII. 170 To describe an almicanther and azimuth circle. 1783Martyn Geog. Mag. I. Introd. 37 Almicanters are parallels of altitude. 1837Whewell Induct. Sci. (1857) I. 178 The circles of the spheres termed almacantars and azimuth circles. 1863W. Chauvenet Man. Spherical & Pract. Astron. I. i. 19 Small circles parallel to the horizon are called almucantars. 1923D. Clark Plane & Geodetic Surv. II. ii. 83 The almucantar, or small circle of equal altitudes.
2. A telescope fitted with horizontal wires and mounted on a float resting on mercury, used for observing the rising and setting of stars.
1880S. Chandler in Sci. Observ. III. No. 5. 36, I propose to call the instrument [for the determination of time and latitude] the ‘Almacantar,’ from an Arabic astronomical term, now obsolete in its general use. 1901Proc. Durham Philos. Soc. II. 6 In the Almucantar we claim that the telescope turns with faultless truth about its theoretical axis of rotation. 1920Nature CV. 329/1 The almucantar, in which horizontality is secured by the device of floating the whole in a mercury bath.
3. Comb. almucantar-staff. (See quots.)
1706Phillips Almacantar-staff, a Mathematical Instrument usually made of Box or Pear-tree, with an Arch of 15 Degrees, to take Observations of the Sun at the times of its Rising and Setting; in order to find the Amplitude, and consequently the Variation of the Compass. 1876Chambers Astron. 91 Almacantar Staff, an instrument formerly used for determining the amplitude of an object. |