Richard,

Thanks for those. I'm having trouble keeping up with the processing of
my images but I do have a stack using the C11 taken about 30 mins before
your I Band image. Mine are unfiltered so the tails merge but you can
see a lot of common features in the attached. This is L-S filtered with
r=4, theta=15deg. The L-S filter is very powerful but can often
introduce artefacts if you are not careful. It is good to see similar
results from two different systems with, presumably, two different L-S
settings. What parameters did you use?

It looks like another clear night here tonight so that will be three
nights in a row. It will be instructive to look at changes
night-to-night. We also need imaging from other longitudes to fill in
the gaps.

Nick.

On 22/07/2020 15:54, Richard Miles - rmiles.btee at btinternet.com (via
baa-comet list) wrote:
> Imaging with two filters, a B filter having a passband of 370-510 nm and
> a Sloan i passing 700-850 nm allows a comparison of the dust and gas in
> the inner coma.
>
> The two images from observations made last night, which have been
> subjected to the same Larson-Sekanina processing, are remarkably
> different in several aspects.
>
> The dust image shows a short spiralling jet beginning somewhere around
> p.a. 0° and spiralling anticlockwise through an angle of about 210°.
> The same feature in the gas coma appears to move outwards about 2x
> faster than the dust one and spirals anticlockwise more than 400°.
>
> Notice also the two prominent tails that emanate from either side of the
> pseudonucleus, whereas the dust is a much more mixed feature.
>
> The dust envelopes are at different distances from the nucleus than the
> gas ones. Also the dust envelopes are sort of parabolic in shape whereas
> the gas are generally circular centred on the nucleus. This circular
> symmetry extends much further outwards than shown here when seen in the
> ordinary light image
>
> At a solar elongation of 35°, phase angle of 103° and a distance from
> Earth of 0.69au, we are having a favourable apparition of Comet NEOWISE.
> That we see distinct spirals in the inner coma means that we must be
> seeing the nucleus relatively close to 'pole-on' and that there is one
> active region on the nucleus that is producing a large fraction of the
> outflowing material in a continuous fashion lasting perhaps many days.
>
> Richard