R.H. McNaught discovered a comet near the border of the constellations Lepus/Columba on Aug. 20, 2006. Comet C/2006 Q1 (McNaught) was of magnitude 17.5, displaying a 20" coma with a weak central condensation, but no tail. Currently this comet is still far from the sun, reaching perihelion not before mid-2008. Assuming an average brightness evolution it should reach magnitude 11-12 in spring 2008 (IAUC 8742). In this case it would be brighter than 15.0 mag from summer 2007 until summer 2009. For mid-European observers it will be positioned low above the southern evening horizon during April/May (moving through Antlia and Hydra). From December 2008 to summer 2009 it would be a well-positioned object moving through Virgo, Serpens and Hercules. The analysis of this comet, which was only visible low above the southern evening horizon in April/May 2008 and again starting at the end of 2008 for mid-European observers, could use 7 observations of 2 members of the German Comet Section and 65 international observations. The brightness evolution can be described by the formula m = 4.8m + 5×log D + 10.2×log r, yielding a maximum brightness of 11.2 mag at the end of April 2008. The coma diameter increased considerably from 0.5' (70.000 km) at the end of 2007 to 2.8' (300.000 km) in mid-May 2008. It then shrunk, measuring only 0.8' (150.000 km) at the beginning of 2009, a value still valid at the end of May 2009. The coma was medium-condensed (constant at DC 4) until Feb. 2009. Thereafter it grew more diffuse, with the degree of condensation only DC 1 at the end of May 2009.
Total Brightness and Coma Diameter
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On May 6, 2008 E. Beshore discovered a 13.8 mag comet, using the 1.5m Mt. Lemmon Telescope, near the border of the constellations Ophiuchus and Serpens. Comet P/2008 J2 (Beshore) showed a diffuse 20" coma and a faint tail at least 20" long in p.a. 250°. The determination of the orbit proved surprisingly difficult and led to a few considerable changes of the orbital elements. According to the recent elements the comet orbits the Sun within 6.5 years and passed its perihelion at the end of March (IAUC 8941/44 und MPEC 2008-M03). The maximum brightness of 13.0 mag was reached in June/July 2008, the coma diameter reached 2-3', however the estimates showed a very large scatter (12.5-14.0 mag / 0.5-5').
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Comet 7P/Pons-Winnecke (P=6.36a) peaked at magnitude 11.0 in September 2008 - 1.5 mag brighter than expected. The diameter of the medium-condensed (DC 4) coma measured 2'.
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International observations of comet 15P/Finlay (P=6.50a) indicated a maximum brightness of magnitude 10.0 in mid-July 2008 - 2.5 mag brighter than expected. Surprisingly, during the following weeks the comet faded only very slowly, reaching 11.0 mag at the beginning of September. Thereafter, however, no further positive observations have been published. Thus the actual brightness evolution is very confusing. The diameter of the rather diffuse (DC 3) coma was in the order of 2-3'.
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According to 15 published observations of comet 19P/Borrelly (P=6.85a) it peaked at the predicted brightness of 9.3 mag at the beginning of August 2008. The brightness evolution cam be described by the formula m = 5.0m + 5×log D + 20.5×log r. The diameter of the medium-condensed (DC 3-4) coma measured 6' (550.000 km) at the start of the apparition, decreasing to 2' (175.000 km) till the end of September. At the start of 2009 the coma measured 1.2' (100.000 km).
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J.J. Gonzalez could glimpse comet 26P/Grigg-Skjellerup on the morning of Apr. 6, 2008. He estimated it to be of magnitude 11.3, showing a very diffuse (DC 2), 2.8' coma - very typical for this object. According to the very small number of observations the brightness evolution confirmed the proposed brightness parameters (m0=12.5m/n=4). Thus it reached magnitude 11.5 at perihelion (Mar. 23, 2008). Thereafter it faded, reaching magnitude 13.5 at the beginning of June. The coma measured about 3' at the beginning of the observations and 1' at the start of June, with the coma being very diffuse.
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According to the very few published observations, comet 61P/Shajn-Schaldach (P=7.05a) evolved as predicted and peaked at about 14.5-15.0 mag in fall 2008.
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On Sep. 10, 2008 the Japanese amateurs Koichi Itagaki and Hiroshi Kaneda discovered a bright comet of magnitude 13 near the border of the constellations Aquarius/Aquila on patrol images taken with a 21 cm reflector. On the CCD images it showed a strongly condensed 25" coma and a 2' tail pointing east-southeast. Maik Meyer was the first to identify the comet as P/Giacobini (1896 V). Comet P/2008 R6 (Giacobini) has passed perihelion 17 times since its discovery, passing Earth at a distance of only 0.51 AU on Sep. 9, 1962 and Jupiter at only 0.81 AU on Jan. 14, 1992. On Sep. 17 two fragments were found; the brighter fragment B, 4 mag fainter than the main component A, was situated 70" west and 5" south of the latter, the fainter fragment C, 5 mag fainter than the main component, was located 660" west and 60" south of it. Their positions may be calculated using the main components elements, applying dT=+0.014d for B and dT=+0.133d for C. According to Z. Sekanina component B separated from the main component during the second half of 2006, component C already at the end of 1998. In the meantime the comet has received the final designation 205P/Giacobini (IAUC 8975, 8976, 8978, 8980, 8987, MPEC 2008-S47). For a first analysis only 20 observations could be used. These show no plausible brightness evolution. However, the estimates indicate a maximum brightness of 12.5-13.0 mag in mid-September 2008, with the moderately condensed (DC 4) coma measuring about 2'.
Andreas Kammerer
