The project comet 1999 of the german comet section, 10P/Tempel 2, did not come up to expectations. Also, observations were difficult due to its southern declination, resulting in only 28 reports from 6 FG members until the beginning of February. Adding 215 international observations makes it possible to make reliable statements. Comet Tempel 2 always was a difficult object since its coma expanded in accordance to the increase in brightness, keeping the surface brightness at low level. Only the central condensation could be seen fairly well in a 30 cm telescope. Therefore an aperture correction was applied to the brightness estimates.
The brightness evolution shows the known distinction between a steep increase pre- and a shallow decrease post-perihelion, with the change taking place at perihelion at this apparition. In addition the comet showed the well-known time dependent term:
This yields a maximum brightness of 9.4sup>m around perihelion. The apparent coma diameter was around 1' at the start of the apparition, reaching 3.5' around perihelion, decreasing to 1.5' at the start of January 2000. Contrary, the absolute coma diameter increased continually from 45.000 km to 160.000, but halting at this value during the last weeks. The coma was not very condensed, the degree of condensation seems to show a very slight decrease from DC 3-4 to DC 2-3 during the apparition.
Total Brightness and Coma diameter
Andreas Kammerer
