Comet 6P/d'Arrest update

We imaged again periodic comet 6P/d'Arrest on 2008, July 11.96, from the Remanzacco Observatory (click on the image for a bigger version):

Image processing show the possible presence of a tiny coma, nearly 20 arcsec in diameter. The crowded stellar field hampers a sure identification of this feature, however this faint "halo" moves with the proper motion of the comet; moreover, the FWHM of the comet appears to be significantly larger compared to that of neary field stars of similar brightness, and this seems to confirm the presence of a detectable coma. The brightness of the comet has been measured at about magnitude 15 (Ru). This is still somehow fainter compared to the ephemerides (that indicates instead a visual total magnitude m1 equal to about magnitude 14), however we do know that i) CCDs magnitudes are frequently fainter than visual magnitudes and ii) the lightcurve of 6P/d'Arrest is known to show a striking asymmetric lightcurve, with lower pre-perihelion brightness. The Afrho parameter is still rather low (about 16-cm for a radius of nearly 3,000 Km at the comet distance).

Updated ephemerides are available (as always) at the Minor Planet Center website.

Giovanni Sostero and Ernesto Guido

Periodic Comet 6P/d'Arrest

This comet has been recovered during its current return to perhelion by J. Hobart (Kachina Observatory) on 2008 Apr. 29.37, through a 0.36-m f/11.2 Schmidt-Cassegrain + CCD, while it was slowly moving in Ophiucus at m2~ 19.5.

It is supposed to became a relatively easy telescopic object in a few months from now; perihelion will be reached on 2008, August 14, while perigee will occour few days earlier).

We performed some follow-up observations on 2008, June 9 (details on image; click on it for a bigger version):

In our stackings it appears as a faint starlike object (red magnitude close to 18) while it moves in a very rich Milky Way's star field in Aquila. Due to the star crowding, it is nearly impossible to distinguish any potential weak coma, if present.

by Giovanni Sostero & Ernesto Guido