Chasing Venus: Observing the Transits of Venus 1631-2004
What is a Transit of Venus?
Discovering the Transits: The 1631 and 1639 Transits
Measuring the Universe: The 1761 and 1769 Transits
New Possibilities: The 1874 and 1882 Transits
The Transits of 2004 and 2012
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Chasing Venus: Observing the Transits of Venus, 1631-2004

Discovering the Transits of Venus

Eyre Crowe (1824-1910)
Jeremiah Horrocks Watching the Transit of Venus in 1639
Courtesy of National Museums Liverpool (The Walker)

Jeremiah Horrocks Watching the Transit of Venus in 1639

Crowe painted this picture 250 years after Horrocks’s death. Horrocks and his telescope are depicted according to Victorian tradition and astronomical practice. Horrocks was not a sickly Puritan curate, and his equipment would have been set up in a similar way to Crabtree’s.

Discovering the Transits of Venus

Pierre Gassendi (1592-1655)
"Mercurius in sole visus & Venus invisa". Opera omnia (Mercury seen upon the Sun & Venus unseen)
Florence: Typis Regiæ Celsitudinis …, 1727. Volume 4
Gift of the Burndy Library

Opera omnia

Gassendi, a French astronomer, was one of a few witnesses of the first recorded planetary transit—Mercury’s on November 7, 1631. He shows Mercury’s path across the Sun as a series of black dots. Gassendi noted that the predicted transit of Venus one month later did not occur. Kepler’s tables had neglected to indicate that the transit would take place after the Sun had set for European observers.

Discovering the Transits of Venus

Johannes Hevelius (1611-1687)
Mercurius in Sole visus (Mercury seen upon the Sun)
Gdansk: by the author, 1662.
Gift of the Burndy Library

Mercurius in Sole visus

Kepler thought that Venus would pass below the Sun in 1639, but Jeremiah Horrocks calculated that it would indeed transit the Sun. Consequently, Horrocks and his friend William Crabtree were the first witnesses of a transit of Venus. Unfortunately, because Horrocks died suddenly in 1641, his observations went unpublished until 1662, when the astronomer Hevelius, in his book on the 1661 transit of Mercury, printed Horrocks’s work for the first time.

Discovering the Transits of Venus

Jeremiah Horrocks (c. 1617-1641)
Transit of Venus across the Sun
London: William Macintosh, 1859?.
Gift of the Burndy Library

Transit of Venus across the Sun

Horrocks, a gifted English astronomer and mathematician, might be better remembered if he had not died in his early twenties. When he predicted the 1639 transit of Venus, he lived in Hoole, north of Liverpool, and set up his telescope in his home to watch the transit on December 4. Not sure of the precise time of the transit, he checked the Sun regularly. At 3:15 PM he saw Venus as a “spot of unusual magnitude and of a perfectly circular shape” on the Sun. This translation of Horrocks’s posthumously published Latin work, is open to the pages where he tells of his first sight of the transit.

Discovering the Transits of Venus

Johannes Kepler (1571-1630)
Tabulæ Rudolphinæ (Rudolphine Tables)
Ulm: J. Saurii, 1627.
Gift of the Burndy Library

Tabulæ Rudolphinæ

The Rudolphine tables (named for the Holy Roman Emperor Rudolf II) were the crowning achievement of Kepler’s career. These astronomical tables allowed astronomers to compute the positions of the planets, and Kepler used them to predict the 1631 transit of Venus. Kepler is pictured in the panel at the bottom left of this illustration, which depicts an allegorical temple of the heavens built on the foundations of the great astronomers’ works.

Discovering the Transits of Venus

Christoph Scheiner (1575-1650)
Rosa Ursina (The Rose of Orsini)
Bracciani: Andream Phæum, 1630.
Gift of the Burndy Library

Rosa Ursina

Scheiner, a Jesuit in Italy, was an expert at studying the Sun and a vocal opponent of Galileo. In this book (titled after his patron, the Duke of Orsini, whose family emblem was the rose), Scheiner shows how to view the Sun indirectly using a telescope. Pointing the telescope at the Sun and letting the image shine through the eyepiece to focus on a white screen was the preferred 17th-century way of observing the Sun, including transits of Venus.