Attached is a plot of the current astrometry that I have since November
13. I asked Denis to remeasure his images from November 14 at I81 and
they now all show a large positive RA residual for the main component
which is consistent with the I79 residuals from November 13.

The plot shows the residuals for the main component as filled circles.
The triangles are the residuals for component B. These residuals are
from the fitted orbit using astrometry prior to November 4.

Nick.

On 15/11/2025 11:00, Nick James wrote:
> This comet was reported to have fragmented on or about November 4 (ATEL
> 17482, 17487, 17488). Recent astrometry shows a significant residual (6
> arcsec on Nov 13) in the position of the main component when compared to
> the orbit solution using astrometry up to November 4. This may be
> biasing of the centroid, but this screenshot shows the measurement I
> made on the morning of November 13 and the main component looks very
> well defined so I don't think that is the case. The radius of the
> aperture is 4.5 arcsec. This observation was made using the Alnitak
> telescope in Spain (I79) and Denis Buczynski got similar results on the
> morning of the 14th.
>
> If anyone has any recent (post November 11) astrometry of this comet
> please forward it to me and the MPC. Astrometry of the main fragment
> (C/2025 K1-B) would also be very useful. It is now well separated from
> the main component.
>
> Thanks,
>
> Nick.