Richard,

Thanks. Could you explain a bit more about the characteristic Pacman
shape that we are seeing?

Presumably the eruption is effectively an impulse and the material then
expands almost symmetrically in a hemisphere above the surface. The coma
expansion rate is 200 m/s or so which is an order of magnitude or more
times the escape velocity so I would expect most of the material to
travel away in straight lines so we would see an expanding hemisphere
from some external angle. I don't see how that causes the shape we
actually see.

I know I can probably go and read your Icarus paper but a short summary
would help!

Nick

On 23/11/2020 17:55, Richard Miles - rmiles.btee at btinternet.com (via
baa-comet list) wrote:
> Nick - Great image showing the discontinuity between the star-like
> pseudonucleus and the ever-expanding visible coma.
>
> No joy with 2.0-m images due to bad weather.
> However, provided you build the SNR as you have with a longish
> time-series, your images can provide data almost as good given suitable
> seeing and focus. This becomes increasingly the case as the coma expands
> because amateurs have the luxury of sitting on a target for a long time
> whereas access to the 2.0-m is only for a limited few minutes. At least
> we got a good result with the FT South just 19 hours after the outburst
> started - that's where the 2.0-m really scores well.