Page 223 - Art In The Age Of Exploration (Great Section on Chinese Art Ming Dynasty)

clutching small spheres. A meridian-circle permits This accurately-engraved large planispheric
the adjustment for latitude of the globe, and azi- astrolabe belongs, with cats. 120 and 122, to the
muths can be read from the 360° circular scale group of instruments bequeathed in 1493 to the
surrounding the globe on the horizon-plate, Jagiellonian University by Martin Bylica. It is
which also carries a small compass, for orienting dated 1486 on the alidade, six years after the
the globe, and a horizontal sundial with a string- celestial globe (cat. 120), and is attributable to the
gnomon. A small circular scale of hours is at the same maker, Hans Dorn. Like the other instru-
north celestial pole on the meridian-ring. Over it ments, it is engraved in fine Roman antiqua let-
moves an index fixed to the axis of the globe tering. It bears, on the back of the suspension
below the turning-handle. Once adjusted for lati- piece, the coat of arms of Bylica, and the Latin
tude, rotation of the globe simulates the apparent words MARTINI PLEBANI, indicating Bylica's
rotation of the stars about the celestial pole at the possession.
place of use, thereby providing a didactic or ana- The astrolabe is the best known of the astro-
logue computing device. For the resolution of nomical instruments of Islam (cat. 112) and
other astronomical or astrological problems, there medieval Europe; many have survived. It reduces
is an astrolabe mounted vertically on an arc atta- the image of the celestial sphere to a plane surface
ched to the horizon-plate at right angles to the using an ingenious geometrical procedure: stereo-
meridian. It includes a plate of the twelve astrolo- graphic projection as described in Ptolemy of
gical houses, with a rete consisting solely of the Alexandria's Planisphderium from the second cen-
ecliptic circle, and a plate engraved with an tury A.D. The astrolabe was known early in Islam
orthographic universal astrolabe projection. This and transmitted from Muslim Spain to medieval
projection, known today as the Rojas projection — Christian Europe no later than the twelfth cen-
after Juan de Rojas who published an account of it tury. The astrolabe is usually too small to make
at Paris in 1550 —is very rare in medieval manu- serious astronomical observations but was useful
scripts and on medieval instruments. It was for teaching astronomy, in the practice of astrol-
however used by the Andalusian astronomer, Ibn ogy, and for simple time-telling by night or by
as-Zarqalluh, in eleventh-century Toledo. Dorn's day. The upper cut-away plate, called rete in Latin
use of universal projections on his globe and on and also in Middle English, on the front of the
his astrolabes is innovatory. (For explanations of instrument is a star-map where the tips of the
the astrolabe terms used here, see Bylica's astro- curly pointers represent the positions of selected
labe, cat. 121). brighter stars, which are named in engravings by
The globe is engraved with the equator, the the pointers. On the rete, the eccentrically placed
tropics, the polar circles, twelve meridians, the circle represents the ecliptic, the apparent path of
Milky Way, and thirty-six constellation images — the sun through the stars in the course of a year,
indicating the magnitude of their constituent stars and is divided into the twelve signs of the zodiac,
and, more especially, because of the Roman anti- and the astrological nature of the planetary sym- each sub-divided into thirty degrees. The outer
qua capital letters in which the instruments are bols. This information was derived from the thir- circular band represents the Tropic of Capricorn,
engraved. This style of letter was used in print- teenth-century Latin translation of the Haly (the
ing, for example by Regiomontanus for his Kalen- tenth-century Cairene astronomer, All Abu
der of 1474, but is extremely rare on astronomical Hassan b. Ridwan) commentary on the Tetrabib-
instruments, which in the medieval period are los of Ptolemy of Alexandria from the second cen-
engraved in Gothic (Black Letter) script and later tury A.D. The iconography of the constellation
in standard Roman or italic lettering. The only images is sometimes unusual, using European and
known instrument signed by Hans Dorn, a sil- Arabic sources (Ameisenowa 1959). F.R.M.
vered brass astronomical compendium, dated 1491
(British Museum), is engraved in Roman antiqua
capitals.
Hans Dorn was born between 1430 and 1440;
he became a Dominican and from 1491 he resided
at the Dominican monastery in Vienna where he 121
died in 1509 He was a pupil of the Austrian astrol-
oger and mathematician Georg Peuerbach and of Attributed to Hans Dorn
Regiomontanus between 1450 and 1460 in Viennese, 1430/1440-1509
Vienna. From 1458 to 1490, he was in the service MARTIN BYLICA'S ASTROLABE
of King Matthias in Buda—where, presumably,
Bylica's instruments were made. King Matthias 1486
sent Dorn to Nuremberg from 1478-1479 in an Buda?
attempt, which proved unsuccessful, to buy the brass
2
3
books, manuscripts, and scientific instruments left height 52 (20 /2J; diameter 45 (iy /4J
by the deceased Regiomontanus. references: Rosinska 1974; Pilz 1977, 62-63;
The globe proper, made from a hollowed-out Wattenberg 1980, 343-362; Schallaburg 1982, 33^-
sphere of brass, sits within a square horizon-plate, 339, no. 283; Turner 1987, 35-37
supported by a "Gothic" stand on four claw-feet Jagiellonian University, Cracow

222 CIRCA 1492