Museo Galileo
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Virtual Museum
Section of Room II
Measuring Time by Night: Astrolabes and Nocturnals

Highly versatile instruments, astrolabes could also be used to tell the time by day or by night, based on direct measurement of the height of the Sun or of a star. Astrolabes had been developed to the highest levels by medieval Islamic astronomers. In the 16th century, devices of European design were produced for measuring time by night. Nocturnals, for instance, determined the hour by the position of the last two stars in the Big Dipper in relation to the Pole Star. These instruments were useless when the sky was overcast.

Objects
Astrological disk

Astrological disk

Inv. 2505
Maker unknown, 17th cent.

Astronomical compendium

Astronomical compendium

Inv. 2478
Maker unknown, German, late 16th cent.

Astronomical compendium

Astronomical compendium

Inv. 2481
Maker unknown, German, ca. 1600

Geometrical square

Geometrical square

Inv. 121
Maker unknown, Italian?, 16th cent.

Hourglass (sand)

Hourglass (sand)

Inv. 429
Maker unknown, Italian?, 17th cent.

Lunar converter

Lunar converter

Inv. 3701
Maker unknown, Italian, 17th cent.

Nocturnal

Nocturnal

Inv. 2504
Maker unknown, French, 1560

Nocturnal

Nocturnal

Inv. 2494
Maker unknown, Italian, late 16th cent. - early 17th cent.

Nocturnal

Nocturnal

Inv. 2493
Maker unknown, Italian, mid-17th cent.

Nocturnal

Nocturnal

Inv. 2501
Maker unknown, French, 1554

Nocturnal

Nocturnal

Inv. 2502
Pineau [attr.], French, ca. 1600

Octant

Octant

Inv. 120
Maker unknown, Italian?, 16th cent.

Oil clock

Oil clock

Inv. 3570
Maker unknown, 18th cent.

Perpetual calendar

Perpetual calendar

Dep. MA, Firenze
Christian Boyling, Dresden, second half 17th cent.

Plane astrolabe

Plane astrolabe

Inv. 1096
Hans Dorn [attr.], German, 1483

Plane astrolabe

Plane astrolabe

Inv. 1106
Maker unknown, German?, 16th cent.

Plane astrolabe

Plane astrolabe

Inv. 1107
Maker unknown, French?, 13th cent.

Plane astrolabe

Plane astrolabe

Inv. 1109
Maker unknown, Arab, 14th cent. (?)

Plane astrolabe

Plane astrolabe

Inv. 1105
Muhammad 'Ibn Abi'l Qasim 'Ibn Bakran, Arab, 1102-1103

Plane astrolabe (open)

Plane astrolabe (open)

Inv. 1111
Georg Hartmann, Nuremberg, 1545

Portable quadrant

Portable quadrant

Inv. 2513
Maker unknown, 17th cent.

Portable quadrant

Portable quadrant

Inv. 2513
Maker unknown, 17th cent.

Quadrant

Quadrant

Inv. 1495, 2465
Tobias Volckmer, Braunschweig, 1608

Quadrant with Easter scale

Quadrant with Easter scale

Inv. 2518
Josua Habermel [attr.], German, ca. 1600