Hi Nick,

It is reassuring that there is a band of material associated with the fragment that you saw. I just couldn't see how there could be a single big chunk of stuff out there by itself. It must have been very small with some untapped material. The big chunks are not moving very fast. That is why I was surprised and very skeptical (at first) when a fragment appeared so far ahead of the main fragments.

I appreciate Richard's discussion. He says that material would be sent out in all directions. That probably is not strictly true. There are bound to be one or more favored directions when the split occurred. Afterward, the movement would probably be dictated to some extent by the dynamics within the coma. I am still surprised that the significant material went sunward. However, it is possible that the material is less the result of the split itself and more the end product of an outgassing event. Basically the remnants of a jet. No doubt someone will model all of this and explain it.

I should get the part for my telescope by Thursday - and, of course, it is clear. At least the moon is around so I don't feel that bad.

Best regards,

Charles

On Monday, May 4, 2020, 11:58:16 AM PDT, Nick James <ndj@nickdjames.com> wrote:

Hi Charles,

No confirmation yet and it looks to have been very short-lived. What we
do have is some imaging from iTelescope T24 (a 0.61m, f/6.5 Planewave NE
of Fresno) by Martin Mobberley obtained on May 4.2 which shows material
to the SW of the bright photocentre in the direction of the object that
I observed on May 2.9.

In the attached file the top two panels are Martin's T24 image from this
morning stacked on the stars and stacked on the comet, the bottom panel
is my image from May 2.9 stacked on the comet.

The two systems have similar pixel scales:

Chelmsford: 0.28m, f/10, 18um pixels = 1".29 / pix (FWHM 2".3)
iTel T24: 0.61m, f/6.5, 24um pixels = 1".26 / pix (FWHM 3".4)

I have taken the raw FITS files and processed them as follows:

Each subframe is first processed to subtract the local median pixel
level with a radius of 10 pixels. This removes the general low-frequency
coma and tail background. The resulting frames are then stacked. I have
used 8x60s for Martin's T24 to avoid a star cutting across the area of
interest and 50x60s for mine. The iTelescope stack is a simple sum, my
stack has enough frames to do a sigma clip. The limiting magnitude of
both stacks is around the same (approx SNR of 20 for mag 19.5). As noted
previously the object marked "?" appears on multiple stacks and moves
with the comet.

You can see a train of material to the SW of B on Martin's image which
bridges the gap between B and the component I imaged on May 2.9. This is
hinted at on my image too. The condensation itself appears to have been
transient. These images suggest that there is material spread along a
line sunward of the residual nucleus and on May 2.9 one of these small
chunks became active for a short time.

It would be really good to find some deep images taken around the time I
imaged the object to see if we can confirm this with another system. The
object was around mag 19.

An interesting comet indeed.

I hope your observatory gets fixed soon. I know how frustrating it is
when equipment does silly things.

Nick.

On 04/05/2020 18:36, Charles S Morris - cometguy3783 at yahoo.com (via
baa-comet list) wrote:
> Hi Nick (James),
> Has anyone confirmed your observation?
> I think what you imaged was real, but I still don't understand it. This comet is doing weird stuff I hope to be beck observing by Thursday after my equipment mishap.
> Best,Charles

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