46p 20181210 gvbuitenen

Yesterday I observed 46P/Wirtanen through my 12" dobson for about an hour using various magnifications. Of course the coma appears much smaller in a large instrument, but at moments of good seeing, some subtle details become visible.

First of all it is clearly asymmetrical: A bright, point-like inner condensation appears off-center towards the west. Then the on-set of a tail is most obvious (PA ~40°) but not extending beyond the coma. A second brighter feature was visible extending north towards a mag 12.9 star, perhaps one side of a bow shock(?) because another one could sometimes briefly be seen on the opposite side of the tail. More clearly visible was a brighter region in the east at roughly a right angle to the tail. Probably this is due to the jet that is also seen in the Larson-Sekanina filter images of other members of this group.

Also I tried some filters. 21 Orange was too dark but 11 yellow didn't really help either. The 80A blue helped a little bit on the (apparently gaseous) features, while (quite unexpectedly) the Lumicon swan-band did not.

In the 10x50's, I estimated the comet at m1=4.8 with DC3/ a coma of ~40'. (Ref. stars Tycho2: 641-985-1=4.68, 59-1947-1=4.92, 4722-1534-1=4.71)