An asteroidal object of magnitude 19.5, discovered by Michel Ory on Nov. 12, 2013 with the 0.5m-telescope at Oukaimeden Observatory (Morocco), showed its cometary nature by closer inspection. Comet C/2013 V5 (Oukaimeden) showed a significantly condensed 15" coma of total magnitude 18.3, and a fan-shaped 25" tail in p.a. 300°. It will pass the Sun at the rather small distance of 0.63 AU at the end of September 2014, expected to reach magnitude 5 (CBET 3713). However, during these most interesting days its elongation from the Sun will be rather small. Furthermore it will move through the southern parts of Hydra and Centaurus, being invisible for mid-European observers. For them only a small observing window is offered, from mid-August until the first week of September, with the comet reaching altitudes below 15°. During this interval it will move through Monoceros and should brighten from 10 mag to 7 mag.

For the analysis I could use 165 international observations. These indicate a very different behavior prior and post-perihelion. Whereas the comet brightened very slowly prior to perihelion, the activity was average post-perihelion. The comet peaked at magnitude 6.4 on Sep. 17, the day of closest approach to Earth (distance 0.48 AU). The appropriate formulae are:

Total Brightness and Coma Diameter

The apparent coma diameter increased from 2' in early August 2014 to the maximum of 5.5' around Sep. 25. Immediately thereafter it decreased rapidly again, measuring 2' in mid-October. The derived evolution of the absolute coma diameter was as follows: during August it measured 200.000 km, but decreased to 100.000 km during closest approach to Earth, increasing again to 160.000 km until the end of September. Thereafter it finally decreased, reaching 100.000 km in mid-October. However, physically it is not plausible that the absolute coma diameter should have reached a minimum during closest approach to Earth. It is more plausible that the coma diameter decreased continuously from 200.000 km to 100.000 km between early September and mid-October and that the minimum during perigee was a result of the then suboptimal observing conditions, which did not allow to detect the outer parts of the coma, which may actually have been as large as 12'. The degree of condensation was DC 4-5 until early September, increasing to DC 6 during perihelion, only to rapidly decrease to DC 4 until mid-October. Visual tail observations have been reported between early August and mid-September. It reached a maximum length of 0.5° (some observers even reported 1.0°), yielding an absolute length of 800.000 to 1.5 Mio. km. The tail was oriented westward before perigee, eastward thereafter.

Andreas Kammerer