Hello Nick,

> This latest outburst was a big one but it has had no detectable effect
> (so far) on the motion of the very massive nucleus of 12P. This plot
> shows astrometric residuals from three stations (970, I79 and I81) with
> an orbit fit using Findorb that uses positions up to Nov 14. You can see

this agrees with the fact that when I identified 12P with the comets of 1385 and 1457 the adjustement in perihelion time was just a few days. Despite being very active and having passed four unobserved perihelia between 1547 and 1812, the amount of needed NGF to fit these two apparitions was surprisingly low. So, yes, a rather massive comet.

It will be interesting to see whether the outbursts will continue. I think the early outbursts are driven by a different mechanism/chemistry and possibly the increasing activity closer to the sun may overshadow the outbursts. As a simple model one may assume that the outbursts may also become less frequent or smaller since the outbursts have removed large parts of the insulating dust crust on the comet. Looking at the last good observed apparition of 1954 I see no signs of large outbursts post-perihelion, something that has been mentioned in literature before. On the other hand, the comet was/is mostly in southern skies post-perihelion which means a less close surveillance back then. This is different now.

Regards

Maik
--
"One cannot discover comets lying in bed." * Lewis Swift
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