Copyright © 2007 by John Drummond (Possum Observatory, New Zealand)
J. Drummond took this picture on 2007 March 16 after T. Lovejoy asked him to confirm a possible new comet he had found. He was using a 41-cm reflector and an SBIG STL11000M CCD camera.
Terry Lovejoy (Thornlands, Queensland, Australia) discovered this comet on sixteen 90-second exposures obtained using a Canon 350D and a 200mm lens on 2007 March 15.73. The images were obtained during a comet-hunting survey that Lovejoy has been conducting for over a year. He estimated the magnitude as 9.5. Lovejoy also noted a green coma 4' across, with a strong central condensation and a slight extension toward the southwest. The first independent confirmation was obtained by John Drummond (Possum Observatory, Gisborne, New Zealand) on March 16.53. He used a 41-cm reflector and visually estimated the magnitude as 9.5 and the coma diameter as 2.6'.
A very preliminary parabolic orbit was published on March 16 by Maik Meyer. Using semi-accurate positions spanning less than a day, it indicated a perihelion date of 2007 March 7.76 and a perihelion distance of 1.17 AU. Meyer wrote, "Needless to say that this is a mere guess and the actual orbit will be quite different." The first official orbit was calculated by B. G. Marsden (Central Bureau, Cambridge, Massachusetts, USA) on March 18. He took 36 positions spanning three days and determined a perihelion date of March 27.57 and a perihelion distance of 1.09 AU. Marsden's orbit indicated that Meyer's early orbit was a rather good representation of the comet's orbital plane considering that it was based on such a short arc.
Numerous visual observations were made in the days following the discovery announcement. On March 16, Andrew Pearce (Nedlands, Western Australia, Australia) observed using his 41-cm reflector (90x) and gave the magnitude as 9.5. He said the coma was 2.5' across. On the 17th, Pearce observed using the same telescope and gave the magnitude as 9.6 and the coma diameter as 3.0'. Jim Gifford (Bridgetown, Western Australia, Australia) observed using 25x100 binoculars. He gave the magnitude as 10 and the coma diameter as 2'. On March 18, Stuart Rae (Hamilton, New Zealand) observed using a 25-cm reflector. He gave the magnitude as 9.3 and the coma diameter as 2.7'. On the 20th, Rae observed with the reflector and gave the magnitude as 9.3. He said the coma was 2.2' across. On the 20th, Rae observed using his reflector. He gave the magnitude as 9.3 and the coma diameter as 2.2'. On the 24th, Drummond observed using an 8-cm refractor. He gave the magnitude as 8.7 and the coma diameter as 4.5'.
The green color indicates an abundance of cyanogen and diatomic carbon. The comet's orbit indicates it will move steadily northward and will pass closest to Earth during the last half of April. The maximum magnitude might reach 7, making it an easy object in small telescopes.
Copyright © 2007 by Terry Lovejoy
T. Lovejoy (Thornlands, Queensland, Australia) combined eight 90-second exposures using his Canon 350D and a 70-200 zoom lens set to 200mm, with the average date being March 15.73. North is left and the scale is 6.8"/pixel. The comet is near the top and was near the edge of the frames. He wrote, "The comet was so conspicious that I noticed almost immediately in the individual 90 second raw frames."
Copyright © 2007 by Rolando Ligustri