The most interesting comet of 1999, C/1999 H1 (Lee), which was discovered by an Australian amateur in the constellation Musca on April 16, 1999 at magnitude 9 during a star party. Not only because it was an easy object in binoculars, but also because of the appearance of the predicted anti-tail. First reports date from the beginning of August and the anti-tail got brighter during the following 2-3 weeks, when it appeared more prominent than the gas tail (for example I was able to see only the anti-tail visually!). The anti-tail was at an angle of 150° to the main tail at the beginning, but shifted towards the solar direction by the end of August.
Based on 151 observations by members of the German comet section and 725 international observations the brightness evolution can be described by one formula:
yielding a maximum brightness of 6.0m at perihelion and an observable maximum brightness of 6.5m.
Regarding the evolution of the coma diameter, two identical maxima of 12' were observable under a moonless sky (mid May and September/October). The apparent diameter at perihelion should have been around 3-4'. The absolute coma diameter increased from 250.000 km to 450.000 km. The latter value was kept until the end of October, when it decreased within a short period of time to 220.000 km and then, until Jan. 2000, slower to 180.000 km. The coma was well condensed during several months. The DC value increased from DC 4 to DC 6-7, when the comet disappeared in the twilight. After perihelion the value was DC 5-6, decreasing slowly to DC 1 in December.
Pre-perihelion a 0.5° (2 million km) long gas tail was observed visually. Post-perihelion photographic observations revealed a gas tail that grew rapidly fainter. At the same time an anti-tail evolved which grew longer and brighter during the following weeks, much easier recognized by visual observers than the gas tail. The maximum post perihelion gas tail length was observed to be 0.3° visually (about 1 Mill. km) and 2° (4 Mill. km) photographically. For the anti-tail the lengths were 0.5° and 1°, respectively.
Total Brightness and Coma diameter
Andreas Kammerer
