Copyright © 1970 by H. M. Maitzen, A. Moffat, and H. E. Schuster (La Silla, Chile)
This image was obtained by H. M. Maitzen, A. Moffat, and H. E. Schuster (European Southern Observatory, La Silla, Chile) on 1970 May 23.97. It is a 10-minute exposure using a Leica M3 camera attached to a 24-inch reflector. The bright object on the right-hand side of the image is Venus, which was overexposed during the exposure. Special thanks go to Graeme L. White for bringing this image to my attention, Roger Sinnott of Sky and Telescope for providing the scanned image, and Dr. Maitzen for giving me permission to use this image on my web site.
Graeme L. White (Barrack Point, New South Wales) discovered this comet with 12x50 binoculars on 1970 May 18.32. He said the head was starlike, with a magnitude of 1-2, while a tail extended about one degree. White tried to confirm his discovery from Sydney Observatory on May 19.33, but, although he strongly suspected seeing the comet, city lights prevented him from being sure. White finally confirmed his discovery on May 20.33, with both binoculars and the naked eye. He estimated the magnitude as 2, and said the tail extended over 10 degrees. His estimated positions indicated a rapid eastward motion. Dr. Harley Wood (Sydney Observatory) sent a cable to the Central Bureau on May 21. A few hours after receiving this cable, the Central Bureau received a cable from Tananarive, Malagasy Republic, reporting the discovery of a comet by Air France pilot Emilio Ortiz (Orly, France) on May 21.63. Ortiz estimated the magnitude as 0.5-1.0, and estimated the tail length as 5 to 8 degrees. Based on White's two rough positions, the Central Bureau sent out an extrapolated ephemeris to Argentina, South Africa, Australia, New Zealand, and the southern United States. On May 22, Karl Simmons and R. Sweetsir (Florida) could not detect the comet, and in Arizona, Elizabeth Roemer and others also failed to detect it. More than two days passed without additional word of the comet, but finally Betty Mintz (U.S. Naval Observatory, Washington, D.C.) relayed a report from V. M. Blanco (Cerro Tololo Interamerican Observatory) that Carlos Bolelli (Cerro Tololo) had discovered a bright comet on May 21.95. Bolelli said the head was then below the horizon and no position could be obtained; however, on May 22.97, he again saw the comet and gave a rough position. He estimated the magnitude as 1 and said the tail was 10 degrees long.
A large number of independent discoveries were also reported during the next few days.
- Alberto O. Bernhardt (a student at Lucas González, Argentina) accidentally found the comet on May 22.9 and noted a narrow tail.
- H. M. Maitzen and Hans-Emil Schuster (European Southern Observatory) discovered the comet on May 22.96, then subsequently learned that F. Gomez (a technician in charge of meteorological observations at the observatory) observed the comet's tail on May 21.9.
- Stewart (110km north of Wellington) discovered the comet on May 23.25. He said the tail extended at least 10 degrees.
- F. W. Gerber (Lucas González, Argentina) discovered the comet on May 23.9. He said the tail extended 15 degrees.
- H. Potter (National Observatory, Santiago) discovered the comet on May 23.95. A few minutes later he estimated the magnitude as 4 and said the tail extended over one degree.
- An independent discovery was made by Jorge Balseiro Savio (Mercedes, Uruguay) on May 23.96. He estimated the magnitude as 3-4, and said a tail extended 15 to 20 degrees.
- G. N. Sprott (Smithsonian Astrophysical Observatory station at Woomera, South Australia) discovered the comet on May 24.38. He said his photograph revealed a stellar head of magnitude 4, and two tails, the southern one bright and straight and the northern one much fainter and curving to the north. Sprott said the tail was visually estimated as 12 degrees long.
- Kellie (Port Hedland, Western Australia) discovered the comet on May 24.45.
Numerous observations were obtained on May 24. Although most observers were in agreement that the comet's tail was 12 to 15 degrees long, estimates of the brightness ranged from 1 to 4, possibly because of the relatively low altitude. The tail was described as narrow near the coma, but becoming slightly wider and diffuse near the end. There was a starlike nucleus within the coma.
As May came to an end, observers' estimates of the comet's brightness were in better agreement, with values between magnitudes 5 and 6. Also in agreement was the fact that the tail length had declined to about 5 to 7 degrees. B. G. Marsden (Central Bureau for Astronomical Telegrams) computed the first rough orbit before the month ended. He said early positions were inconsistent, but he suspected the comet was a Kreutz sungrazer. By assuming the direction of perihelion he determined a perihelion date of May 14.5 and a perihelion distance of 0.0090 AU.
As June began the comet continued its fading and became more diffuse. Magnitude estimates ranged from 6 to 8 on the 1st and 2nd, to 7 to 8.5 by the 6th. The tail length may have been as great 7 degrees on the 1st, but dropped to just over 2 degrees by the 6th. Part of the brightness and tail length decline were due to the increasing moonlight. Subsequently, the comet was last detected on June 7.34 by M. V. Jones. He described it as a faint, ill-defined nebulosity. The observation was made with a 20-cm reflector under good observing conditions, although there was some interference from moonlight.
As precise positions continued to come in, Marsden continued to revise the comet's orbit and confirmed his suspicion that it was a sungrazer. His first revision came on June 18 and another came on July 19. On the latter date he determined the perihelion date as May 14.49 and the perihelion distance of 0.0089 AU.