Boyden Observatory through the 60″ Rockefeller Reflector

The 60-inch Rockefeller Reflector is one of the main telescopes at Boyden Observatory, currently located in Bloemfontein, South Africa. It all started when Uriah A. Boyden, a mechanical engineer in Boston, MA, donated $238,000 to Harvard College in 1879 to extend astronomical research. With the newly acquired money, Harvard declared its need for an observatory in the southern hemisphere, mainly to study the Magellanic Clouds. The original site was in South America. After an expedition encouraged by Edward Pickering, a hill near Chosica, Peru was chosen. The hill was fittingly named Mount Harvard. The equipment was carried inland to Mount Harvard by mule, along with the daily supply of food and water. The Boyden Observatory started taking photographic plates of the southern hemisphere on May 9, 1889. However, unstable weather at Mount Harvard prompted a relocation to Arequipa, Peru in October 1890 .

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The Boyden Observatory at Arequipa, Peru.

Meanwhile, in Ealing, UK, Andrew Ainslie Common was also working to extend astronomical research. In 1885 he began building a 60-inch Newtonian reflector telescope. His first mirror performed poorly, so he built a second, changing the design instead to a Cassegrain telescope. A Newtonian reflector consists of a concave primary mirror that focuses light at a specific point. Since one could not view the focused light from the top of the telescope without blocking the sky, a secondary mirror is added, which is flat and diagonal to the oncoming light, thereby reflecting it to the side of the telescope where easy viewing can be achieved. However, looking high up on the side of a large telescope is not always possible. A Cassegrain telescope has a similar concave primary mirror, but the secondary mirror is convex and directs the light through the bottom of the telescope. In order to achieve this, one must drill a hole in the primary mirror. Since the mirror took so much work, Common didn’t want to drill a hole in it for fear of cracking it, so he put in another (tertiary) diagonal mirror. The telescope was not used often because of the less than satisfactory images it produced.

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Andrew Ainslie Common

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Common’s telescope in Ealing, UK

In Arequipa, many discoveries were made by HCO because the southern hemisphere sky could finally be viewed and recorded.  Henrietta Leavitt, a famous woman astronomer of Harvard, used the plates from Peru for her research. Research here also helped lead to the discovery of the Period-Luminosity relationship for Cepheid variables, along with discoveries of novae, asteroids, and variable stars. Once again, unstable weather and an inability to effectively communicate with Harvard prompted another relocation, this time to Bloemfontein, South Africa.

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 Boyden Observatory at Bloemfontein, South Africa.

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 Locations of the Boyden Observatory

Harvard and the International Education Board each donated $200,000 for the move. Observations at the new location began in September 1927. For the new location, Harvard bought and reconfigured Common’s telescope using funds from the Rockefeller family. They re-figured the primary mirror and installed a new mount, built by J.W. Fecker, in 1933, and in 1940 the telescope was brought to Bloemfontein.

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The 60” Rockefeller Reflector at Bloemfontein, South Africa

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Locations of the Common mirror / the Rockefeller Reflector.

Up until the 1960’s, however, the telescope still had an inadequate mirror and systems, and all discoveries made with it should be accredited solely to the talent of the operators, not the precision of the telescope. An overly  complex system of pulleys and counterweights allowed the operator to move the telescope. The reflector’s primary purpose was to take photographic plates of NGC1844, a cluster in the Magellanic cloud. The telescope used both Kodak 103a-D and Kodak 103a-O plates, with various filters. It has a focal length of 1218 cm, and a scale of 17 seconds of arc per millimeter. The main telescopes in operation at Bloemfontein were the 60 inch Rockefeller reflector (SB series), the Boyden refractor (X series), and the Metacalf refractor (MF series), all of which are currently in located there. Several other smaller telescopes were used, but are no longer in use. In 1954, Harvard could no longer justify the expenses of the establishment, so the Boyden Council was formed to keep it alive. In the 1960’s, the observatory became a tool to track the Soviet Union’s progress in the space race. Harvard withdrew from Boyden Council in 1976. Soon all members withdrew, and it was left to be owned by the University of the Free State, a University in South Africa, who owns it today. At UFS, the 60-inch reflector is currently used for education and for amateur astronomers. Images from the Reflector were used for news broadcasts of the Jupiter Shoemaker-Levy 9 impacts in 1994. In the 1990’s the 60-inch Reflector was upgraded by UFS with a new mirror from Custom Optics. Several other modifications were done, such as a stronger mirror cell to hold the new mirror, which is 1000 pounds heavier than Common’s mirror.

[Thomas Rhines and David Sliski]

Sources:

Studies of the Large Magellanic Cloud VII. The Open Cluster NGC 1844

Andrew Ainslie Common Wikipedia

The Irish Astronomical Journal Vol. 10. Boyden Observatory: A Brief History of the Observatory

Boyden Observatory Then and Now by H. J. Heerden

The Boyden Observatory by A. D. Andrews. Irish Astronomical Journal