In mid-July 2012 comet 96P/Machholz (P=5.28^a) will again reach its perihelion at the very small solar distance of just 0.12 A.U. at a predicted maximum brightness of about 3 mag. However, at this time it will be too close to the Sun to be observable. Starting on July 25 mid-European observers may try to observe it in the evening twilight, very low above the northwestern horizon. It will then be positioned near the border of the constellations Leo and Leo Minor, predicted to be of magnitude 7. At that time the coma should still be well condensed. During the following days the coma becomes quickly fainter and more diffuse. Around Aug. 20 the comet will reach the maximum altitudes of this apparition of about 15°. Then moving through the northern parts of Virgo it is predicted to have faded to 13 mag.

The apparition of 2012 was less favourable than that of 2007, during which several members of the German Comet Section succeeded in observing it. Therefore it is comprehensible, but nevertheless surprising, that only one observation was reported by one member of the German Comet Section. Me too, I did not succeed on two trials. Because only 25 international observations came to my knowledge, this analysis is based on a very small data base. The brightness evolution was as expected: a very rapid brightening pre-perihelion followed by a slower fading post-perihelion as the following formulae indicate:

They indicate a calculated maximum of 4.0 mag at perihelion. Pre-perihelion the comet brightened from 13.0 mag on June 20 to 10.0 mag during the first days of July. The first post-perihelion observation was reported for July 23, when the comet was of magnitude 7.8. During the following days the comet faded rapidly, reaching 9.5 mag on Aug. 1, 11.5 mag on Aug. 16 and 12.5 mag on Aug. 23.

Total Brightness and Coma Diameter

The coma diameter increased from 0.5' (25.000 km) around June 20 to more than 3' (150.000 km) around Aug. 20. Pre-perihelion the estimates of the degree of condensation are inhomogeneous (hinting to DC 5). Post-perihelion the degree of condensation decreased steadily from DC 5-6 to DC 2-3. No visual tail sightings were reported.

Andreas Kammerer