Forms: 4– astrolabe; 4–5 astre-, astrylabe, astre-, astra-, astro-, astrilabie, -labye; astre-, astro-, astel-labre, astro-laboure, 5 astyllabyre, astyrlaby, 6 astroloby, -ie, 7 astralobe (astrolable). [a. OF. astrelabe, and ad. med.L. astrolabium, f. Gr. ἀστρολάβον (in same sense), orig. adj. ‘star-taking’ (sc. instrument), f. ἄστρον star + λαβ- take. The forms in astre-, etc., were of OF. origin, as also the ending -labe; -labie, -laby, was prob. adaptation of med.L. -labium, and -labre of a med.L. corruption *-labrum, after candelabrum, etc.]
An instrument formerly used to take altitudes, and to solve other problems of practical astronomy.
The actual form and structure of the astrolabe of course varied greatly with the progress of astronomy, and the purposes for which the instrument was intended; its most complex form, as described by Tycho Brahe, passed into the modern EQUATORIAL. The chief types were the following:
a. A portable ARMILLA, or arrangement of armillary circles.
b. A planisphere, representing the circles of the heavens in the plane of the equinoctial, with movable sights.
c. A graduated brass ring with movable label or index turning upon the center, used simply to take altitudes (the Sea Astrolabe).
1366. Maundev., xvii. 180. I my self have mesured it by the Astrolabre.
c. 1386. Chaucer, Miller’s T., 23 (Harl. MS. c. 1415). His almagest … his astrylabe [other 15th c. MSS. astrelabie, -labre, astellabre, astro-laboure]. Ibid. (c. 1391), Astrol., Prol. 1. To lerne the tretis of the astrelabie … A suffisaunt astralabie as for owre orizonte [also, passim, astrolabie, astrilabie].
1393. Gower, Conf., III. 64. With him his astrolabe he name, Which was of fine gold precious With points and cercles merveilous.
c. 1440. Promp. Parv., Astyllabyre, instrument (1499 Astyrlaby], Astrolabium.
c. 1525. Skelton, Speke Parrot, 137. In the astroloby To pronostycate.
1594. Blundevil, Exerc. (7th ed.), III. II. viii. 387. Having taken the Meridian altitude … with your Astrolabe or Quadrant.
1594. J. Davis, Seaman’s Secr. (1607), 2. The Astrolabie and Quadrant being instruments very vncertaine for Sea observations.
a. 1626. Bp. Andrewes, Serm. (1856), I. 255. Never a Chaldean of them all could take it with his astrolabe.
1834. Penny Cycl., II. 525. Hipparchus is the first who can be supposed to have made use of an astrolabe.
1837. Whewell, Hist. Induct. Sc., III. iv. § 3 (1857), I. 156. To ascertain the position of the sun with regard to the ecliptic … an instrument called an astrolabe, was invented, of which we have a description in Ptolemy.
