Copyright © 2009 by Robert H. McNaught (Siding Spring Observatory, Australia)
A. Milner reported the discovery of a comet on four images obtained with the 1.0-m reflector of the Lincoln Near Earth Asteroid Research (LINEAR) program (New Mexico, USA) on 2004 December 7. The earliest of these images was obtained on December 7.08, while the latest was obtained on December 7.11. The magnitude was between 18.7 and 19.1 during this period, while an possible tail extended toward PA 90 degrees. The first reported confirmation was obtained by E. J. Christensen (Catalina Sky Survey, Arizona, USA) on December 9.10. His 68-cm Schmidt reflector revealed a total magnitude of 16.2-16.6, a coma diameter of 8" and a faint tail extending 20" in PA 60 degrees.
The first orbit was published by B. G. Marsden on 2004 December 9. Using 14 positions from the period of 2004 December 7-9, Marsden calculated a parabolic orbit which revealed a perihelion date of 2004 November 7.37. He wrote, "It is possible that this comet is of short period." Marsden published a revision on December 18, which used 61 positions from the period of December 7-15. The result was a perihelion date of November 2.81 and a period of 5.98 years. A further update was published by Marsden on December 24, which gave the perihelion date as November 2.21 and the period as 5.15 years. Following the comet's recovery in 2009, the orbit for the 2004 apparition was recalculated and was found to have a perihelion date of November 1.92 and a period of 4.83 years.
The comet steadily faded after its discovery, as it was moving away from the sun. Its elongation was also decreasing, so that the total period of observation was barely over a month. It was last detected on 2005 January 11 by S. Gajdos (Modra).
Apparition of 2009: During the course of the Siding Spring Survey, R. H. McNaught (Siding Spring Observatory, Australia) found an asteroidal object on four images obtained on 2009 June 29, while using the 0.5-m Uppsala Schmidt and a CCD camera. The earliest image was obtained on June 29.47, while the last was on June 29.49 and the magnitude was given as 18.1-18.3. The comet was independently confirmed on June 30 by McNaught and R. Ligustri (RAS Observatory, Moorook, South Australia, Australia).