Index:

Visiting; Associated.

List of Visiting Astronomers:

Baily, Francis
Dixon, Jeremiah
Elkins, W
Johnson Manuel
Mason, Charles
Newcomb, S           Photo Gallery
Wales, William

Mason and Dixon

Two English Astronomers, Charles Mason and Jeremiah Dixon were on their way to Bencoolen in Sumatra to observe  the 1761 transit of Venus. Their ship was delayed so they did their work at Cape Town instead.  The transit was successfully observed from Concordia Gardens, a social club that used to be behind  St Mary's Cathedral in Cape Town. In 1772 Wales and Baily used the same site to do observations in Cape Town.

Mason and Dixon, became well known for their land survey between Maryland and Pennsylvania (U.S.A.), known as  the "Mason and Dixon line". This line was surveyed to settle legal squabbles between the two states. During the American Civil War this line came to represent the dividing line between the slave owning and non-slave owning states (Confederates and Yanks)

Mason, Charles:

Dixon, Jeremiah:

Sources: - Mason and Dixon

Remaining Artefacts:

Bibliography:
Koorts, W.: The 1882 transit of Venus: The British expeditions to South Africa; MNASSA April 2004, Vol. 63 nos. 3 & 4, pp. 34 - 57.
Laing, J.D. (ed.), The Royal Observatory at the Cape of Good Hope 1820  - 1970 Sesquicentennial Offerings.
Moore, P. & Collins, P., Astronomy in Southern Africa, p  (General  Source)
Smits, P., A Brief History of Astronomy in Southern Africa. (Unpublished)

Wales and Baily

Two English Astronomers, William Wales and Francis Baily accompanied Captain Cook on his second voyage in 1772. They set up their telescope in Concordia Gardens, a social club that used to be behind St Mary's Cathedral in Cape Town-close to the spot used for this purpose by Mason and Dixon.

Wales, William:

Baily, Francis:

Also known as Bayly
Born: 1774
Died: 1844

Famous for:
-He  first observed the phenomena that became known as "Baily's  Beads".  It can be observed during a total eclipse of the sun.
-President of the Royal Astronomical Society.

Sources: - Baily

Remaining Artefacts:

Bibliography:
Laing, J.D. (ed.), The Royal Observatory at the Cape of Good Hope 1820  - 1970 Sesquicentennial Offerings.
Smits, P., A Brief History of Astronomy in Southern Africa. (Unpublished)

Elkins W L (later Dr.)

Elkins was an American student who stayed in Strasbourg. He came to Cape  Town in January 1881 to pay Sir David Gill a short visit. He ended up staying for 2 years and 4 months. He helped Sir David Gill with heoliometer parallaxes measurements of nine southern stars, including Alpha Centauri. (Pioneering work as this was the first ever systematic measurement).Elkins worked with the Dun Echt Heliometer.

Sources: - Elkins

Bibliography:
Moore, P. & Collins, P., Astronomy in Southern Africa, pp.74 - 75.
Koorts, W.: The 1882 transit of Venus: The British expeditions to South Africa; MNASSA April 2004, Vol. 63 nos. 3 & 4, pp. 34 - 57.

Johnson Manuel

Johnson: Manuel John
Manuel John Johnson was a Lieutenant in the St. Helena Artillery and had been appointed by the British East India Company to be in charge of the Observatory on St. Helena Island. To gain experience he visited Fearon Fallows at the Cape Observatory from 29 December 1825 until 5 March 1826 and again from 12 September 1828 until 7 March 1829, during the opening ceremony of the Cape Observatory. He helped Fallows with pendulum experiments.
He produced a valuable catalogue in southern stars in which he acknowledges the help of Fallows in the introduction. This catalogue earned Johnson the Gold medal of the Royal Astronomical Society in 1835. Johnson was also Radcliffe Observer at Oxford, 1839 - 59.
Johnson noticed that Alpha Centauri has a large relative movement in Space. That means it must be close to Earth. When Henderson visited him at St Helena, he mentioned the fact to Henderson. This conversation led Henderson to measure the first stellar distance by parallax method (to Alpha Centauri), but he did not publish it.  Friedrich Bessel measured the distance to 61 Cygni and published it first.

Sources: - Manuel

Bibliography:
Warner, B., Astronomers at the Royal Observatory Cape of Good Hope.

Newcomb Simon (Prof)

1835 - 1909

Newcomb was an astronomer at the US Naval Observatory (USNO), and became the most honoured American astronomer of the 19th century - a crater on the Moon was even named after him.

With the 1882 Transit of Venus America decided to send an expedition under the leadership of Newcomb to South Africa. Gill originally suggested Beaufort West as an observing site. When Newcomb heard about the American connection with the Huguenot Seminary at Wellington he decided to go there instead.

At Wellington Newcomb's party had fine weather and reported after the Transit that "… all our observations were successful". William Harkness reduced the observations and obtained a value very close to the accepted modern value. However, Newcomb (as well as Gill) were early critics of the Transit of Venus method to determine the Sun-Earth distance. He also spent a large proportion of his career studying the motion of the Moon and measuring the speed of light. In 1896 he adopted an extensive system fo astronomical constants, which was still in use well into the twentieth century. Newcomb received the Bruce Medal in 1898.

Sources: - Newcomb

Bibliography:
Koorts, W.: The 1882 transit of Venus and the Huguenot Seminary for Girls; MNASSA October 2003, Vol. 62 nos. 7 & 8, pp. 198 - 211.
Koorts, W.: The 1882 transit of Venus: The British expeditions to South Africa; MNASSA April 2004, Vol. 63 nos. 3 & 4, pp. 34 - 57.

Associated Astronomers:

This section is dedicated to important astronomers who were never in Southern Africa but has an important association of some sorts. The association will be explained.

List of Associated Astronomers:

Leavitt, Henrietta

Leavitt  Henrietta

Index: History; Instruments; Sources.

Famous for:
Discovered the variation in the periods of Cepheid stars which became the  standard for the "Period-Luminosity Law".

Summary:
Henrietta  Leavitt made a very important discovery using photographic plates taken by the Metcalf 10-inch refractor. She has never been to  South Africa (to my knowledge). The Metcalf telescope used is now housed at Boyden Observatory, Bloemfontein.  Due to the connection between her and the telescope she is mentioned here.

Historical background:

History:

 The Magellanic Clouds. What are they? Superficially they look like broken-off parts of the Milky Way, but they were obviously  of great importance and at Arequipa (first Boyden Observatory in Peru), many photographs of them were taken with the Metcalf 10-inch refractor. The plates were sent back to Harvard for analysis and a member of the staff, Miss Henrietta Leavitt, began to study  them. She was particularly interested in the Cepheids,  of which there were plenty to be found.
Miss Leavitt concentrated on the Cepheids in the Small Cloud of Magellan  and made a surprising discovery. Due to her work, the "Period-Luminosity Law" was established & she discovered the standard candle (light intensity) to be used to measure distances. "...  she could measure the periods of the Cepheids by comparing plates taken on different nights; and she found that the Cepheids with  longer periods were always brighter than Cepheids with shorter  periods. There was a definite relationship, and the significance of it could hardly be over-emphasised, because to all intents  and purposes the Cepheids in the Small Cloud were at the same  distance from us, just as for most practical purposes it may be said that Johannesburg and Pretoria are the same distance from  New York. Therefore, if the Cloud Cepheids were equally distant,  then those, which looked the brighter, must actually be the brighter.  It followed that the real luminosity of a Cepheid could be found  merely by measuring its period of variation. Because the Cepheids in the Cloud are no different from Cepheids anywhere else, it became possible to measure relative distances". [Copied from  Moore, p.127.]
"Shapley,  at Harvard, was quick to take advantage of this "Period-Luminosity  Law". He studied the Cepheids in the great assemblages of stars known as globular clusters, which lie around the edges of  our Galaxy; he measured the distances of the Cepheids, and hence  the distances of the globulars; and he was able to draw up the first reliable scale-map of the Galaxy. Later, in 1923, Edwin Hubble at Mount Wilson, in California, studied the Cepheids in spiral nebulae, and was able to prove that these remarkable objects are independent galaxies, far beyond  our own. Since then the Cepheids have played a vital role in all studies of the distribution and distances of stars and  galaxies. Inevitably there have been complications; for instance  there was an error in the basic Cepheid scale which did  not emerge until the 1950s, and in a famous paper delivered to  an enthralled audience in London the late Walter Baade doubled the size of the universe "at a stroke". But  everything depended upon the Period-Luminosity Law, and it was  the Metcalf telescope which took the essential photographs."  [Copied from Moore, p.127.]

Career:

Personal:

Instruments:

Henrietta Leavitt reduced photographic plates taken with the Metcalf telescope.

Sources: - Leavitt

Remaining Artefacts:

Bibliography:
Moore, P. & Collins, P., Astronomy in Southern Africa, p.127.   (General Source)

By Leavitt:

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