Hinc itur ad astra


Lotter, T. C. Sphaera armillaris; Instrumentum artificiale orrery ab inventore appellatum. Augsburg, 1774.

German cartographer, engraved astronomical instruments – sphaera armillaris and planetarium with a comprehensive instruction of instrument structure and use

Armillary sphere (lot. sphaera armillaris) – astronomical ring instrument, in other words, spherical astrolabe or spherical celestial model to establish the position of stars and planets on the celestial dome. It was known and used by astronomers from Antique times. In the centre of the instrument is the Earth, surrounded by  three main rings: Zodiac or ecliptic (lot. ecliptica; great circle of celestial sphere showing the path that the Sun traces during the year, circle centre, divided into 12 months with names of Zodiac constellations, each sign - 30˚); the meridian (lot. meridies, where  north and south poles of the celestial dome are marked ) and the  horizon or celestial equator (lot. aequator; equally distant from  celestial north and south poles and separating the visible part of the sky from the invisible part.). Ecliptic and celestial equator intersection points are considered points of the Sun equinox. In spring this point is in Aries constellation, in autumn – in Libra constellation. Other rings: Tropic of Capricorn (Lat. tropicus Capricorni, tropicus Cancri; two circles parallel to the equator ring, showing how far the Earth moves each year from the equator to the North and to the South), two polar circles (Lat. circulus Arcticus, circulus Antarcticus; rings distant from the north and south pole – 23˚30´ and the  equator – 66˚30´). Many circles have graduation into degrees.

Planetarium – mechanical model of solar system and planet movement. The name orrery appeared when the English maker of mechanical instruments Georg Graham (1674–1751) constructed a rotating solar system scale model by order of the 4th Earl of Orrery Charles Boyle (1676–1731). Later mechanical solar system models were called the common word – orrery