A team of scientists from the United States’ National
Aeronautics and Space Administration (Nasa) are on their way to Limpopo to observe next week’s solar eclipse.
The boffins, accompanied by a reported nine tons of equipment, will be hoping for better luck than a previous American expedition to Africa.
In 1889 the US government, under authority of a special act of Congress, sent a scientific expedition on the USS Pensacola to Cape Ledo in Angola to observe the total eclipse which was to occur on
December 22 that year.
The vessel was loaded with twelve tons of astronomical
instruments, a gaggle of scientists that included experts in anthropology, terrestrial physics, language and botany, and a guard of marines to prevent any local cannibals eating the scientists.
The instruments were operated by a pneumatic organ-valve system developed in New York. The scientists reached the site two weeks ahead of the event and
set up camp. Herman Davis, an assistant astronomer with the expedition, described how by ”hard work on the part of all” including the officers and crew of the Pensacola, they got the apparatus in place on shore.
They also managed to make a change of 30 centimetres in the length of their 12-metre telescope tube when at the last moment it was found to be too short and giving no well-defined image.
By the early hours of the morning December 22, everything was fixed ”as well as possible under the circumstances” and the expedition members retired to rest until sunrise.
”At 5.30 (am) the eastern sky became of a ruddy tinge, showing prospect of a beautiful day,” wrote Davis.
”At six, it was a little obscure and remained so till 11.45, at which time the sky cleared and the sun came out very bright, raising the temperature exceedingly.
”During all our stay at Cape Ledo the characteristic of the weather was rain all night, cloudy mornings with rain occasionally and a very bright sun in the afternoon.
”Seeing it therefore become so clear at noon as usual, our hearts grew light.”
As the shore party ate lunch, the Pensacola steamed out to sea, to lie in the path of totality twenty miles offshore.
”We felt that the critical moment was drawing near. The eclipse was to begin according to calculation at about 1.30pm, and totality at 2.56, lasting 3 minutes 9 seconds, the eclipse itself ending at 4.12.
”At 1.15 every man was at his post. Prof. Todd, assisted by Messrs. Wright and Carbutt, took charge of the double-polar axis and the eighteen instruments erected on it.
”Mr. Jacoby, in addition to winding our chronometer, which was sure to stop every four minutes unless constantly rewound, had charge of the 74-foot Brashear mirror.
”Prof. Abbe with a corps of naval cadets took his position on the beach prepared for meteorological work and for sketching the corona.
”Prof. Bigelow assisted by myself was stationed at the 12-metre direct photo-heliograph which was to be in operation during the entire eclipse while the others were to run only while total darkness lasted.
”Alas! how vain are earthly hopes even when centred on celestial objects.
”During totality the sun and moon were entirely obscured by clouds, shutting from our gaze all that beautiful halo of light — the corona –which flashes out around the dark moon and can be seen only during a total eclipse.
”Yet of the various phases we obtained 110 photographs, which, however, I fear, owing to the clouds, will be of no scientific value. Thus, however hard it may be to do so, we must pronounce the expedition a failure so far as astronomical results are concerned.”
The Pensacola made her way slowly back, to report clouds where she had been as well.
After the anticlimax, the ship headed south to Cape Town, where the disappointed scientists did the tourist thing, Davis visiting the leper colony on Robben Island and the diamond mine at Kimberley.
The South African Weather Service is forecasting fine weather for the Limpopo lowveld on December 3, but an ominous ”partly cloudy becoming cloudy” on December 4, the day of the eclipse.
The Nasa website says eclipse-watching weather is statistically likely to be better in Australia, though that will be offset by a shorter eclipse period and the low altitude of the sun.
In Africa, it suggests Beitbridge as best bet.
There it says, the ”relatively high sun angle and convective nature of the cloudiness, which will be at a minimum for a morning eclipse, suggest a probability of success around 60%”. – Sapa