Riding the wave

Southern Sky
History of Ephemerides and constellations

by Vincenzo Gaggero

The Italian Navy Hydrographic Institute (Istituto Idrografico della Marina) published the Ephemerides (nautical almanac) for the first time in 1916. They provide the daily astronomical positions at given times of 66 celestial bodies, including the Sun, Moon, Venus, Mars, Jupiter and Saturn, while in the appendix there are monthly data of over 150 stars, and tables of various kinds.

The word derives from the greek Ephemeris = journal, diary, book where the positions of celestial bodies were recorded.

The current Ephemeris are very accurate, providing the astronomical coordinates with the precision of a tenth of a minute, and are used to calculate the ship position, the transit of the stars at the meridian, the rising and setting of the sun and moon, and the duration of twilight. At twilight it is possible to see the brightest stars and the horizon, and measure their height on the horizon with a sextant.

Today's accuracy and the present names and identification of the constellations and stars result from millennia of astronomical observations, from the improvement of the astronomical instruments first designed by the astronomer Tycho Brahe, at the end of 1500, and finally from the invention of the telescope that has allowed greater precision.

Since ever, all peoples on Earth have observed the sky for practical purposes such as measuring time, compiling calendars and fixing reference points fot their acitivities at sea and on land, and have assigned names to the Sun, the Moon, the planets, the constellations and the stars.

The International Astronomical Union in 1922 establshed the position and names of 88 constellations; the names of the oldest ones mainly derive from mythology - Mesopotamian, Greek and Arabic - while modern constellations (especially those observed by the astronomer-abbot Lacaille between 1751 and 1752) have the names of tools and instruments invented at that time.

The names of the stars may have the following sources:

1. Position within the constellation: Denebola (from the Arabic Al Dhanab al Asad = Tail of the Lion), Menkar (from the Arabic Al Minhar = nose of the whale etc ....) Most star names have this origin.

2. Proper Names: Arcturus, Canopus, Castor, Pollux, Regulus, etc. ...

3. Contraction of the Greek letter attributed to the star, and the Latin genitive of the name of the constellation: Acrux = Alpha Crucis (the brightest star of the Cross), Atria = Alfa Trianguli Australis (the brightest star in the Southern Triangulum)

4. Name of astronomers: the two major stars of theDolphin, were named for the first time in the Catalog made in Palermo in 1814; Alpha Delphini under the name of Rotanev and Beta Delphini under the name of Sualocin. These two names, if read backwards, become Nicolaus Venator, which is the Latinized name of Nicholas Hunter, assistant to Father Giuseppe Piazzi, director of the Observatory of Palermo who took over when Father Piazzi went to the Observatory of Naples.

5. In the Thirties of the twentieth century, the British Royal Air Force (RAF) asked the Nautical Almanac Office (NAO) to produce an almanac for aviation, similar to the Nautical Almanac, but with detachable sheets so that pilots could take just the pages they needed. The RAF wanted all the stars to have a proper name and thus two stars in the Southern Hemisphere, not included in the "Alamagest" and without a proper name (Epsilon Carinae and Alpha Pavonis) become Avior (Latin word meaning " The furthest") and Peacock.


In the 3rd millennium BC, the Astronomers in Mesopotamia, began to systematically record the names of the stars on clay tablets.

This knowledge reached Crete, the heart of Mediterranean civilization, which in 1450 BC was swept by a huge tidal wave, caused by the earthquake that ripped through the nearby island of Santorini. The survivors took refuge in Egypt where astronomy was intensly studied, and could resume their astronomical interests.

Thales of Miletus (624 to 546 BC), after his visit to Mesopotamia, studied the celestial sphere and the ancient constellations.

Eudoxus of Cnidus (408-355 BC), described 45 constellations of the northern sky and built an astronomical observatory.

During the 3rd century BC, Alexander the Great invaded Egypt and Asia Minor, in 338 BC founded Alexandria, and in that new cultural pole Greek knowledge fully aboserbed the culture of Persia, Mesopotamia and Egypt.

In that same period Aristarchus of Samos was the first to present the heliocentric theory that would be developed by Copernicus, and was published in 1543.

Aratus (315 to 245 BC) commented on the work of Eudoxus, in his Phaenomena (phenomena), translated into Latin by Julius Caesar Germanicus, added two constellations to the 45 identified by Eudoxus, and gave proper names to some stars (including Arcturus).

Eratosthenes of Cyrene (276 to 194 BC), director of the Library of Alexandria, calculated with good accuracy the circumference of the Earth, invented the astrolabe (later improved by the Arabs) and, in his book Katasterismoi, described the constellations and the pertinent Greek myths.

Hipparchus of Nicaea (185 - 125 BC) developed a celestial sphere with the coordinates of 1087 stars, identified by their brightness; furthermore, by comparing these coordinates with those calculated by Timocharis and Arystillus, he measured the shift of the equinoctial points, and formulated the theory of the Precession of the equinoxes (which was already known, though empirically, to the ancient astronomers.

Claudius Ptolemy (100 - 178), librarian in Alexandria, around 140 published the book "Mathematics syntaxis", which was translated in Arabic as "Al Magisti (meaning "the Great") - in the Middle Ages known as "Almagest" - where he listed 48 constellations and catalogued 1022 stars. Ptolemy's writings have come down to us thanks to the translation made by Gerard of Cremona in the 12th century.

Of the 48 constellations identified by Ptolemy, 47 appear in modern astronomical catalogs, because the ship Argo was split in mid-1700, by the French Nicolas Louis de Lacaille in 4 constellations: Carina, Puppis, Pyxis and Sails.

Ptolemy also gave names to some stars: Aetus (Altair), Antares, Basiliscos (Regulus) and Lyra (Vega) and for each star described its position within the Constellation. His descriptions were accepted by the Arabs and translated in their language.

With the fall of the Roman Empire, many Western scholars took refuge in Gonde-Shapur in Persia, an important cultural center, occupied in the 7th century by the Muslims who encouraged the study and translation of Western classics into Arabic.

New centers of astronomical research were Damascus (founded by the Umayyad caliphs) and then Baghdad (founded by the Abbasid caliphs). The Caliph of Baghdad, Al Mamun (786-833), son of Harun al-Rashid, created the House of knowledge, where he hosted Western scholars and was thus accused of being the "Commander of the unbelievers." In Baghdad, worked many astronomers, including Albategno who compiled the science of stars.

The Persian City Suzi, in the 11th century, under the sultans Soldjuk, became an important cultural center, birthplace of Al Sufi who cataloged 1018 stars in his "Description of the fixed stars.

In the Middle Ages the following tables were published, with the astronomical coordinates of the stars, which can be considered the forerunners of the current ephemeris:

a) Cairo: Kakemite Tables

b) Toledo: Tables of Azarchel

c) Maharajah (Persia): Tables on-khaniche

d) Castile: Alphonsine Tables (named after King Alfonso X of Castile) compiled in 1272, where, for the first time, the long Arabic names of stars were contracted and Europeanized.

e) Samarkand: Zig tables of 1437, with the astronomical coordinates of the stars, approximated to the tenth of a degree.

f) Germany: Rudolphine Tables (named after the Emperor Rudolph II) published by Kepler in 1627 in Ulm, which reported the astronomical coordinates with the precision of 1 ' (the former had an accuracy of 30', the apparent diameter of Sun and the Moon) and took account of the elliptical shape of the orbits.

The Dutch cartographer Gerardus Mercator, in his Celestial Globe of 1551, added Coma Berenices to the 48 Ptolemaic constellations.

The Dutch theologian and cartographer Petrus Plancius charged his chief pilot Petrus Theodorus Keyser to observe the stars in the Southern Hemisphere and in 1598 published a Celestial Globe, where he added 12 constellations of which 11 were accepted in 1922 by the International Astronomical Union: Apus (Bird of Paradise), Chamaeleon (Chameleon), Dorado (Golden Fish), Grus (Gru), Indus (Indian man), Hydrus, Pavo (Peacock), Phoenix, Austral Triangulum (Southern Triangle), Tucana (Toucan), Volans (Flying Fish).

The constellation which was not admitted in 1922 was Bee (Apis). On the globe a thirteenth constellation was added, namely Crux (Southern Cross), very well described in 1516 by Andrea Corsali; Ptolemy had placed the stars of the Centaurus Crux.

Johann Bayer, German astronomer and lawyer, published in 1603 the Uranometria, the first great star atlas, with the constellations of Ptolemy, Mercator and Plancius to which he added the constellation Musca (fly). In Uranometria for the first time every star was mentioned both by its name, and by a Greek letter followed by the Latin genitive of the name of the constellation.

The Greek letter was attached with the following criteria: the brightest star in the constellation was attributed (with some exceptions) the letter "alpha", the letter "beta" was assigned to the second bright star and so on and this method is still applied.

Plancius Petrus in 1613 published a celestial map, where headded 7 new constellations of which 3 were accepted by IAU in 1922: Camelopardalis (Giraffe), Columbia (Dove) and Monoceros (Unicorn).

Julius Schiller introduced in 1627 the "Coelum stellatum Christianum" where the classical constellations were replaced with figures drawn from ancient and New Testament: for example, Bootes became St. Silvester, the 12 zodiacal constellations became the 12 apostles, etc. ... But this work was not taken into account by the Roman Church.

The Polish astronomer Johannes Hevelius (name Latinized as Johannes Hevel) invented new constellations, using the astronomical observations of Sir Edmund Halley from the Island of St. Helena. In 1690 his atlas Firmamentum Sobescianum (in honor of John III Sobieski king of Poland) was published posthumously.

In 1922 the International Astronomical Union accepted 7 new constellations, as follows: Canes Venatici (hunting dogs, Lacerta (Lizard), Leo Minor (Little Lion or Leo Minor); Lynx (Lynx); Scutum (shield) - the original name being Scutum Sobiesii, in honor of the King of Poland John III Sobieski; Sextans (Sextant); and Vulpecula (Vulpecula) - the original name being Vulpecula cum Anser, Fox with a goose.

In 1725 the catalog was posthumously published of the first English Royal Astronomer, John Flamsteed, provinding the precise coordinates of 3000 stars and a progrssive number for each constellation, assigned according to their ascension.

In 1750, the French Abbot Nicolas Louis de Lacaille (1713 - 1762) was sent to make astronomical observations at Cape Town, in South Africa, where he set up a small observatory under Table Mountain, which he used from August 1751 to July 1752 .

planisphere of Lacaille
The celestial map of the southern sky by Lacaille

He studied the southern sky with extraordinary precision and, on his return to France, presented in 1754 at the Royal Academy of Sciences, a celestial map (published after two years), with 12 new constellations: Antlia (pneumatic machine) - originally Antlia Pneumatic - Caelum (Burin), Circinus (compass), Fornax (chemical stove), Horologium (Clock - which is shaped like a pendulum clock), Mensa (Table) - i.e., Table Mountain near Cape Town, Microscopium (microscope), Norma (ruler), Octans, Pictor (Painter) - originally Equuleus Pictoris, the Painter Tripod, Pyxis (nautical compass) Reticulum (reticle), Sculptor - originally Apparatus Sculptor, the Sculptor-study, and Telescopium (Telescope).

Lacaille in 1760 published "Southern Coelum stelliferum" with 3 new constellations derived from the splitting of the Ptolemaic constellation "Ship Argo"into Carina (keel), Puppis (stern) and Vela (sails).

Other important cartographers:

Joseph Jerome Le Francais de Lalande (1732 - 1807), who in 1801 designed a numer of constellations including Felis (cat) and Globus Aerostaticum (balloon) that are not among the current official 88 constellations.

Father Giuseppe Piazzi (1746 - 1826), a priest of the Theatine order who, while he was director of the Astronomical Observatory of Palermo, on January 1 1801, with a telescope discovered the first asteroid which he called Ceres Ferdinandea to honor both Ceres, Greek patron goddess of Sicily, and King Ferdinand III of Bourbon. In 1803 he published his first star catalog "Praecipuarum Stellarum Inerrantium Positiones mediae Ineunte Saecula XIX", reissued with great success in 1814, which included 7476 stars with their astronomical coordinates.

Johann Elert Bode (1747 - 1826), Director of the Berlin Observatory, who published, in 1801, the star catalog "Uranographia" with over 100 constellations. This work included, for the first time, all the stars observed with the naked eye, up to the sixth magnitude.

To organize the many extant constellations, the International Astronomical Union (founded in 1919) at its first meeting (Rome, 1922) fixed at 88 the number of constellations. In the following assembly of Cambridge (1925), the Belgian astronomer Eugene Delporte (1882 - 1955) was commissioned to define the boundaries between the constellations: he presented his work in 1928 at the assembly of Leyden, with this news: the traditional boundaries were adjusted curved between the constellations, referring to them instead to follow the lines meridians and parallels of heaven.

The Assembly approved his work published in 1930 and Eugene Delporte "delimitation scientifique des constellations.

Courtesy V. Gaggero,
President 's Cultural Association "The Sextant",
Course Italy 14 / 1 - 16043 Chiavari
website www.ac-ilsestante.it:80/index.html

founded in July 2007