CBET No. 1343, issued on April 20th, announces the discovery by the Lincoln Near Earth Asteroid Research team of a 18.th magnitude comet in Ursa Minor officially designated C/2008 H1 (LINEAR).
It was picked-up on 2008, Apr. 18.34722 with a 1.0-m, f/2.15 reflector + CCD located in New Mexico (USA). After its posting on the Minor Planet Center's 'NEOCP' webpage, several observers performing its astrometric follow-up, reported about its cometary nature: in particular, E. Reina (April 19.0, Masquefa Observatory, Spain) commented about a magn. 16.6 coma almost 25 arcsec in diameter, and a 43 arcsec tail toward P.A. 233 deg. J. M. Aymami (April 19.8, Observatorio Carmelita, Spain) mentioned a suspected coma elongated toward P.A. 209 deg, while R. Apitzsch (April 19.8, Wildberg, Germany) noticed a tail toward southwest.
On April 19.5 we performed our own confirmation images, remotely through a 0.25m, f/3.4 reflector + CCD from the Rent A Scope network (Mayhill station, NM). The sky was clear, however the full Moon increased quite a lot the sky backgound noise; moreover, due to some technical problems, we couldn't stack more than 20 single unfiltered exposures, hampering our detections of very faint details. Anyway, also on our image, below the trail of a faint field's star, it's possible to appreciate the presence of this new comet, with the typical diffuse shape of this kind of objects.
With some image processing, from our image it's possible to notice a central condensation, surrounded by a ~30 arcsec diameter very faint coma, elongated toward South-West (details on image):
A photometric analysis perfomed via Roberto Trabatti's Winafrho software (CARA's dedicated data reduction package), provides m2~ 18 (Ru) for the central condensation, and m1 ~16.5 (Ru) for the total coma brightness. The Afrho parameter (proxy of dust abundance within the coma) upper limit for this comet is then estimated to be nearly 90 +/- 30cm; considering that C/2008 H1 currently is at almost 2.8 A.U from the Sun past perihelium, this result seems to point toward a comet of modest activity.
Preliminary orbital elements published by the Minor Planet Center on M.P.E.C. 2008-H09 show that this object moves along a very elongated and tilted orbit (e= 1, i= 76 deg); perihelion occured on 2008, March 11, with q~ 2.8 AU. According to the ephemerids, for the next few months this object will remain mainly a northern hemisphere target, and it will decrease its brightness from V~ 16.8 to nearly V~ 18.
by Ernesto Guido & Giovanni Sostero
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