A comet was discovered by G. Borisov on Sep. 5, 2014 in the constellation Cancer, using the 30cm-astrograph of Margo-observatory (Russia). According to him, comet C/2014 R1 (Borisov) showed a 30" coma of magnitude 16.0 and a 40" tail. Follow-up observations determined a total magnitude of 14.5 and the orientation of the tail to be p.a. 290°. The comet will reach perihelion if its highly elliptical orbit with a period of about 2.600 years in mid-November and should become as bright as 12.5 (CBET 3968 / MPEC 2014-V27). It will be brighter than 16.0 mag until spring 2015, thereby moving from Cancer near the border of the constellations Ophiuchus/Serpens, being comfortably situated in the morning sky for mid-European observers.
The comet reached a maximum brightness of 10.9 mag at the end of November 2014, as shown by 30 international observation reports. The brightness evolution can be passably described by the formula
m = 7.9 mag + 5×log D + 13.5×log r However, the parameters of the formula have greater uncertainties.Total Brightness and Coma Diameter
The coma diameter decreased continuously during the visibility from 2.5' (230.000 km) to 1.8' (150.000 km). The degree of condensation was rather constant at DC 3-4. Visual tail observations were not reported.
Andreas Kammerer
