IAUC nr.9193, issued on 2011, Jan. 17, announced the discovery of a new comet (magnitude roughly 18) by A. R. Gibbs through the Catalina 0.68-m Schmidt telescope, on images obtained on 2011, Jan. 15.5. The new comet has been designated C/2011 A3 (GIBBS).
After posting on the Minor Planet Center's 'NEOCP' webpage, other CCD astrometrists have also commented on the object's cometary appearance. We performed some follow-up measurements of this object while it was still listed in the NEO-CP, on 2011 Jan. 16.4 and 17.4, remotely from the GRAS Observatory (near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD and with the Tzec Maun Observatory 0.35-m f/3.8.
Our fourteen stacked 120-s unfiltered images taken with GRAS 0.25-m f/3.4 reflector show a sharp coma nearly 8" in diameter (red mag 17.5-17.6) with a faint tail about 15" long toward p.a. 280 deg. While 27 stacked 180-s exposures taken with a Tzec Maun Observatory 0.35-m f/3.8 reflector shows a coma diameter of about 10" with a central condensation and a faint tail about 12" long toward p.a. 280 deg.
Our confirming image (click for a bigger version):
MPEC 2011-B07 assign to the new comet C/2011 A3 the following very preliminary parabolic orbital elements: T = 2011 Oct. 4.469 TT, q = 1.09867 AU, Incl. = 22.805, e = 1.0
According to COCD webpage, this is the 17th comet discovery for Gibbs!!
by Ernesto Guido & Giovanni Sostero
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