Comet Hoenig Heads South

By: Roger W. Sinnott July 23, 2003 0

P. Clay Sherrod of Arkansas Sky Observatory captured this CCD image of Comet Hoenig early on Tuesday morning, July 30th. He used a 12-inch Meade Schmidt-Cassegrain telescope at f/3.75. Note the suggestion of a short, fanned tail toward upper left.

A comet first seen by a German amateur astronomer in July, then lost for five days, is now an easy target for small telescopes in the Northern Hemisphere. This unexpectedly bright comet (magnitude 7.5 or so) is currently moving through Draco, heading toward Ursa Major and Canes Venatici.

It was shortly after midnight on July 22nd that Sebastian Hoenig of Dossenheim, Germany, found himself unable to sleep. So he got up, loaded his Meade 10-inch telescope into the car, and drove to his favorite observing site in the Odenwald woods near Heidelberg. He soon stumbled upon a fuzzy glow just north of the Great Square of Pegasus, in a region he knew to be almost devoid of galaxies and other deep-sky objects. But Hoenig had no star atlas with him — not even a scrap of paper for making notes — so he rummaged through the car and turned up an empty water bottle! Its small white label was just large enough for him to make a careful sketch of the star field. He kept the object in view long enough to determine that it was moving slowly to the north, at about 3 arcminutes per hour.

Later that day Hoenig e-mailed the discovery details to the Central Bureau of Astronomical Telegrams (CBAT) in Cambridge, Massachusetts. But neither he nor any other observer could locate the object again, owing to a very bright Moon and the object's uncertain location. Finally on July 27th, Ken-ichi Kadota in Saitama, Japan, captured a CCD image of the comet 8° north of Hoenig's initial position, thus confirming the discovery. With this find, Sebastian Hoenig becomes the first amateur astronomer to discover a comet from German soil since 1946.

During September this comet is nicely placed in the evening sky for North Hemisphere observers. The chart shows the comet's location at 0 hours Universal Time on selected dates. Click on the image to see the full chart.

Sky & Telescope illustration.

But he's no stranger to comets; he is also credited with locating 20 comets in SOHO spacecraft images of the Sun's vicinity.

Calculations by Brian G. Marsden(Smithsonian Astrophysical Observatory), announced August 6th, indicate that Comet Hoenig will reach perihelion (its closest point to the Sun) around October 2nd. It'll then be situated between the orbits of Venus and the Earth, traveling in a near-parabolic orbit inclined 73° to the plane of the ecliptic.

The ephemeris below gives the comet's right ascension and declination (equinox 2000.0) at 0 hours Universal Time, its predicted magnitude, and the constellation though which it's passing.

Comet Hoenig (C/2002 O4)
Date (0h UT)	R.A. (2000) h m	Dec. ° '	Magnitude	Constellation
Sep 15	12 51.9	+48 56	8.4	CVn
Sep 17	12 48.8	+47 07	8.4	CVn
Sep 19	12 45.9	+45 21	8.4	CVn
Sep 21	12 43.4	+43 38	8.4	CVn
Sep 23	12 41.0	+41 58	8.4	CVn
Sep 25	12 38.7	+40 20	8.4	CVn
Sep 27	12 36.7	+38 43	8.4	CVn
Sep 27	12 34.7	+37 09	8.4	CVn
Oct 1	12 32.9	+35 35	8.5	CVn
Oct 3	12 31.3	+34 03	8.5	CVn
Oct 5	12 29.7	+32 31	8.6	CVn