Uranometria

Origin and history

Cartographic knowledge of the celestial sky has documented millennia of evolution: Babylonians (2000 BC), Egyptians, Greeks (especially Hipparchus in the 2nd century BC and Ptolemy in the 2nd century AD with his Almagest, manual of classical astronomy that dominated Western and Arab astronomy for over a millennium), medieval Arabs (refined the precision of stellar positions; many star names that we use today are Arabic origin: Aldebaran, Betelgeuse, Rigel, Vega, Algol, etc.), medieval Europeans, Tycho Brahe (16th century, his stellar catalogue was the most precise of pre-telescope era).

The famous Uranometria of Johann Bayer was published in 1603 and represents milestone of celestial cartography: was the first systematic complete atlas of the celestial sky, with 51 high-quality engravings of the constellations, including stars of both Northern and Southern hemispheres, with introduction of the Bayer system of star nomenclature (assigning Greek letters of the alphabet to the brightest stars of each constellation in order of luminosity: alpha = brightest, beta = second, etc. — designations that still are used today). Bayer's Uranometria is one of the most beautiful and historically influential celestial atlases ever produced; its colour engravings still are widely admired today as art-science combination.

Subsequent development

After Bayer's Uranometria, important successive cartographies: Hevelius (1690, more star inclusions and improved precision), Flamsteed (1729, star catalogue), Bode's Uranographia (1801), Argelander (19th century, Bonner Durchmusterung — first photometric catalogue of more than 320,000 stars). After the introduction of astrophotography in the late 19th century, celestial cartography was completely revolutionised — modern photographic catalogues contain billions of stars with unprecedented precision. Today the most ambitious modern celestial cartographies (Hipparcos, Gaia European Space Agency missions) are not only mapping with millimetric precision but also measuring movements, distances and physical compositions of millions of stars.

Astrology and astronomy: it is important to distinguish that astrology and astronomy use the celestial cartography for different purposes. Astronomy is the modern empirical-observational science of celestial bodies for purely physical-cosmological purposes. Astrology uses positional knowledge of celestial bodies (especially the planets in the zodiac) for symbolic-archetypal purposes of self-knowledge and guidance. The two share the basic celestial cartography but use it for very different epistemic objectives.

Today

Today: 1) Bayer's Uranometria continues being collectible historical work valued by lovers of celestial art. Quality reproductions are available for those who want to admire it. 2) Modern celestial cartography is freely available through apps and websites: Stellarium (free, beautiful celestial sky simulator), Sky Map, SkyView, Star Walk (apps for mobile that show the visible celestial sky in real time pointing the phone at the sky). 3) For astrologers, the precise positions of planets and stars in the zodiac are calculated with specific astrological software (Astro.com for free; specialised software such as Solar Fire, Sirius). 4) Activity directly observing the night sky is one of the most accessible spiritual experiences — knowing the constellations and the planets gives a sense of cosmic-temporal proportion that complements any spiritual practice.