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Ancient Instruments & Uranometry

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Joined: 28 Mar 2020
Posts: 463

Posted: Mon Aug 02, 2021 4:29 am    Post subject: Ancient Instruments & Uranometry Reply with quote

Engraving of Ptolemy using an Armillary Sphere

Celestial Atlas
by Felice Stoppa

presented by Jean-Pierre Luminet
Directeur de recherches au C.N.R.S.
Laboratoire Univers et Théories (LUTH)
Observatoire de Paris-Meudon


The site run by Felice Stoppa and presented by Jean-Pierre Luminet offers a marvelous visual walk in the enchanted garden of uranometry.
From Piccolomini to Delporte, via Gallucci, Bayer, Cellarius, Hevelius, Doppelmayer, Flamsteed, Bode or Argelander, the most beautiful atlases in history, the most beautiful maps of the sky engraved by human skill and imagination are offered to the Internet user. Faced with such treasures, the mind can only exclaim, repeating the phrase addressed by the Marquise de G. to Monsieur de Fontenelle on the first evening of his Conversations on the Plurality of Worlds (1686): "Teach me your stars. ! "

1) The rich history of the celestial atlases can be broken down into four major periods. Until Bayer's Uranometria (1603), aesthetic and astrological concerns governed the development of celestial charts. The positions of the stars are most often taken from the catalogs of Ptolemy or al-Sufi. The constellations are represented by stylized figures in the tradition of Germanicus, i.e. the Latin translation of Aratos' Greek poem on the constellations, the Phenomena (Phaenomena). The positions of stars are sometimes not indicated, or else incorrectly, conforming to the figurative requirement of an arm, a sword, a face, the outline of a character or an animal mythological, more than astronomical accuracy. This tradition continued during the Middle Ages and the Renaissance. The first printed book illustrated with constellation figures was published in 1482.

2) From the Bayer Atlas to Bode's Uranographia (1801), uranometry is experiencing its golden age. The accuracy of the stellar positions, taken from new catalogs compiled by the best observers, such as Tycho Brahé, is combined with aesthetic concern. Cartographers compete in ingenuity to deliver visions of the sky that are both precise and spectacular.

3) The third period, which begins with the atlas of Bode and ends with that of Delporte (1930), is marked by the professionalization of atlases. If Bode’s Uranogaphia represents the peak of a certain tradition, it also marks the beginning of the split between atlases intended for professional astronomers and those intended for amateurs. The idea of ​​a single large book for everyone, containing everything visible in the sky with easily recognizable figures of constellations, is indeed no longer feasible.

4) Telescopes reveal new celestial objects: stars too faint to be visible to the naked eye, variable stars, new stars, nebulae, which find their place in maps. Precision increases, mythological figures gradually disappear, the advent of photography gives rise to new undertakings. By definitively fixing the constellations, the Atlas of Delporte (1930) opens the modern period. The great censuses (in English, surveys) of the sky carried out with the telescopes of Mount Palomar or the European Southern Observatory (ESO) are materialized by hundreds of photographic plates containing millions of objects. With the development of computers and communication networks, catalogs and atlases are now available online.
In 'Les Cahiers Clairaut No.144 December 2013, Christian Larcher presents some ancient tools used by earlier astronomers. (Note Google translation)

Instruments like
L'arbalestrille (ou baton de Jacob), (The cross-bar (or Jacob's staff)

Jacob's staff, also called a crossbow, is an ancient instrument used for measuring angles in astronomy, then for navigation: the angular distance between two celestial bodies, or the angle between the horizon and a star.
The crossbar, an angle measuring instrument, well known to ship pilots from the 14th to the 18th century, has always lacked precision. The discoveries of the octant and then of the sextant completely took it out of the measuring equipment. There were (illusory?) corrections to be made for fuzzy shadow effects due to angular diameter of the Sun and for the curvature of the Earth for the horizon as a function of the altitude of the observer.

L'astrolabe, (The astrolabe)

The planispheric astrolabe, commonly called an astrolabe (from the ancient Greek ἀστρολάβος, astrolabos, via the medieval Latin astrolabium, "star taker"), is an astronomical instrument of observation and analog calculation. ... A simplified adaptation, the nautical astrolabe, was used for maritime navigation. Remember that the astrolabe is based on a model outdated: geocentrism. However, it allows us to make forecasts with remarkable accuracy.
The eardrum is a metal disc that attaches to the interior of the matrix. An inner circle represents the visible sky.
The circles engraved on the eardrum allow you to find your way in the sky. Those which are graduated from 0 to 90 degrees indicate the height of the star. In another circle is the zenith (90 degrees high)
An eardrum is drawn for a given latitude and the circles passing through the zenith indicate the azimuth.
The hours of the day as well as the cardinal points are engraved on the matrix of the instrument.
The index which looks like a moving arrow graduated in declination can be aligned with the sun and indicates solar time.

There is a story around the Astrolabe. A UK-based wreck hunter claims to have found the oldest known nautical astrolabe, a navigational instrument that guided Portuguese explorers on a perilous journey to India in the early 16th century.
David Mearns told AFP he found the 17.5cm-diameter bronze disc while diving on a wreck off Oman in 2014 but explained that the University of Warwick has only just identified the object, after scanning it.
"When I saw it, I immediately knew it was a very, very important object. I saw a royal coat of arms on it," said David Mearns. "It is the oldest nautical astrolabe", according to this American living in the United Kingdom, dating it between 1496 and 1500, about 30 years earlier than the oldest astrolabe then known.
Mearns' firm, Blue Water Recoveries, found the wreckage in 1998 but did not start excavating it until 2013, together with Oman's Ministry of Culture.
According to Davis Mearns, the wreck is that of a ship called the Esmeralda, which was part of Vasco da Gama's second expedition to India in 1502-1503 and whose captain was the explorer's uncle.
Vasco da Gama was the first European to reach India by sea in 1498, a discovery that paved the way for a period of colonization and trade between Europe and Asia. The astrolabe bore the personal emblem of King Manuel I of Portugal, who took the throne in October 1495. "The Portuguese were at the forefront of developing astrolabes at sea. The oldest reference to their use at sea dates from around 1480," explained David Mearns. Its discovery was placed in the National Museum of Oman.

Le Nocturlabe, (The Nocturnal)

A nocturnal is an instrument used to determine the local time based on the relative positions of two or more stars in the night sky. Sometimes called a horologium nocturnum (time instrument for night) or nocturlabe (in French and occasionally used by English writers), it is related to the astrolabe and sundial. Knowing the time is important in piloting for calculating tides and some nocturnals incorporate tide charts for important ports.
Even if the nightly course of the stars has been known since antiquity, mentions of a dedicated instrument for its measurement are not found before the Middle Ages. The earliest image presenting the use of a nocturnal is in a manuscript dated from the 12th century. Raymond Lull repeatedly described the use of a sphaera horarum noctis or astrolabium nocturnum. With Martín Cortés de Albacar's book Arte de Navegar, published in 1551 the name and the instrument gained a larger popularity.

Les Spheres armillaires (The armillary spheres)

An armillary sphere is an instrument formerly used in astronomy to model the celestial sphere. It was used to show the apparent motion of the stars, the Sun, and the ecliptic around the Earth. The reference system is then the geocentric system also called "Ptolemy system"

Le Quartier de Davis, (Davis Quadrant)

The Davis Quadrant was the first marine instrument invented by Captain John Davis in 1595 for the angular measurement of the Sun above the horizon. It can be considered as the ancestor of the sextant. Manufactured at the time in large quantities, few models are found today.

L'octant ou le Sextant, (The Octant or the Sextant)

The sextant is (nautical) a navigational device for deriving angular distances between objects so as to determine latitude and longitude while octant is the eighth part of a circle; an arc of 45 degrees.

Le Sablier (The Hourglass)

An early device for measuring intervals of time. It is also known as a sandglass or a log glass when used in conjunction with the common log for ascertaining the speed of a ship. It consists of two pear-shaped bulbs of glass, united at their apexes and having a minute passage formed between them.


Last edited by Ouranos on Mon Aug 02, 2021 6:34 pm; edited 1 time in total
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Therese Hamilton

Joined: 22 Feb 2011
Posts: 1745
Location: California, USA

Posted: Mon Aug 02, 2021 4:58 pm    Post subject: Reply with quote

This is an interesting topic, but I'm confused. The book seems to be in French, but then information here on this topic is in English which seems to come directly from pages of the book. Does the book combine French and English?

For anyone interested in old star maps, there's a wonderful book in English packed full in information and illustrations, Star Maps: History, Artistry and Cartography by Nick Kanas. (Praxis Publishing Ltd, 2007) This is probably the best book available on the history of star maps. It's exhaustive in detail.
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Joined: 28 Mar 2020
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Posted: Mon Aug 02, 2021 6:33 pm    Post subject: Reply with quote

Thank you Therese,
The site of Felice Stoppa is Italian by the owner, French by the presenter and most of the old Atlases are in Latin or other languages depending on the origin.
Stoppa's site is a collection of beautiful star maps over the ages.
I used Google Translate for relevant information.
As astrologers, I think we can at least try to bridge the gap with astronomers and understand where we are coming from. Not an easy task I confess!
And thank you for the reference of Nick Kanas

Nice to hear you back in the Forum Therese,

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Therese Hamilton

Joined: 22 Feb 2011
Posts: 1745
Location: California, USA

Posted: Tue Aug 03, 2021 5:36 pm    Post subject: Reply with quote

Ouranos wrote:
Nice to hear you back in the Forum Therese.

Thank you, Ouranos. I think it would be helpful when you translate from French or any other language that you note at the beginning of posts that you are translating yourself or using Google translate since you are quoting someone else's work. The translation may not be exactly as the author wrote it. (Anyway for myself, I'd like a reminder!)
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