ON NIUAFO’OU

Dominion, Volume 24, Issue 54, 27 November 1930, Page 13

ON NIUAFO’OU

Eclipse Expedition

NEW ZEALAND PARTY

Satisfactory Results

Results that were achieved by the party of observers who went from New Zealand to Niuafo’ou Island for the total solar eclipse last month were described by the leader of the expedition, Dr. C. E. Adams, Dominion Astronomer, in an address given last evening under the joint auspices’of the Wellington Philosophical Society and the New Zealand Astronomical Society. It was made clear that satisfactory work had been done and that in the most hazardous part of the scientific programme, flash spectrum photography, these satisfactory results had been gratifying.

Dr. Adams began by explaining how the New Zealand expedition had come into possession of the apparatus it used. The British Permanent Eclipse Committee, he said, had been good enough to entrust New Zealand with the observational work at Niuafo’ou, and had sent out the principal instruments to he used. These were a large coronograph with its coelostat, the identical instruments used by a well-known British expedition in 1919. Of the New Zealand party, Dr. Adams was the only one who had observed a total solar eclipse before. The first total eclipse he had witnessed was a striking one which was visible in Wellington in 1885. The next was one in Australia in 1922, which lasted more than five minutes. On this occasion Dr. Adams had been with an American party. Then in 1925, from the northern extremity of the Dominion, he had observed an annular eclipse. The total eclipse at Niuafo’ou was, therefore, the fourth he had witnessed. Generous Assistance. In the case of the Niuafo’ou eclipse, Dr. Adams continued, the New Zealand party could not have moved without the help of numerous kind friends in the Dominion. The expedition had been proposed at. a time when financial stringency was in evidence, and it had been with regret that the Governmen found itself unable to finance the work. It. had been able, nevertheless, to offer a subsidy on funds that were raised, and when friends of the New Zealand Astronomical Society rallied round after the appeal had been launched, the expedition had been possible. The expedition had been helped, too, by the generosity of many people, including merchants and business firms, the shipping company, which gave concessions and carried instruments and provisions free, and others with whom the party had come into contact. “All of them may rest assured,” said Dr. Adams, “that we are heartily grateful to everyone who helped us.” Setting tip the Instruments. The party made the final stage of the journey aboard H.M.S. Laburnum,, and landed on the island at the north, where the village of Agaha is situated. They found the American party well established —it had been there for six weeks. Suffering at first, perhaps, from a slight inferiority complex, Dr. Adams confessed, the New Zealanders got to work and were able to set up their apparatus on the same flat piece of ground as the Americans. They had been afraid before they left New Zealand that only a hillside would be available, but this was happily not the case. The 19-foot coronograph, which was really a long camera, and its accompanying coelostat, with a 12-inch mirror, were new to all of them, and they had to work out for themselves the details of its erection. In this they met with several difficulties, as well as one or two special difficulties ■which they had not expected to encounter. One was the form in which the base of the coelostat had been made, and another was the fact that the plate-carrier at one end of the long camera could not be brought into focus. All these difficulties, however, they overcame, and by the time of the eclipse the apparatus had been tried and tested many times, and the whole performance rehearsed. For the purpose of adjusting the’ focus of the coronograph it was necessary to use a star whose declination was approximately the same as that of the sun when eclipsed. For this purpose they used the bright star Rigel, in Orion, which rose late at night. Accurate Calculations. Each party had its chronometers, and a “time tent” was established with radio apparatus to receive time signals from Wellington and Washington. Accuraig time was most important for the observers, in case they had. to set their apparatus moving when the sun was obscured. Dr. Adams had communicated with Dr. Comrie, of the British Nautical Almanac office, asking him for any corrections to the elements of the eclipse that were available. These were cabled, out, and were used in conjunction with the accurate determinations of longitude and latitude made by the observers, for the purpose of computing as accurately as possible the contact times at Niuafo'ou.

The results were borne out strikingly when the eclipse was in progress. The time of the first contact differed from the calculated time by less than two seconds, and an even smaller difference occurred with the calculated and observed times of second contact. It was a wonderful agreement, said Dr: Adams. The New Zealand party took four photographs of the corona of different exposures during the brief period of totality, as well as the special flash spectrum photographs. The Americans had a corona programme, a flash spectrum programme, and an Einstein programme, while their cinemamen took a film record of the whole phenomenon. Dr. Adams concluded his lecture by showing biides of the corona and flash spectrum photographs taken on the island. Mr. R. W. de Montalk, who was a member of the New Zealand party, gave" an extremely interesting lecture on the island itself, the natives, and other aspects of the expedition. A film record of the partial eclipse at Wellington was also shown.