I've only just got around to processing my images of C/2020 F3 (NEOWISE)
from July 22. An animation is here:

http://www.nickdjames.com/Comets/2020/2020f3_20200722_ndj.gif

This shows a field of view of 33x22 arcmin processed using a
Larson-Sekanina filter with r=2, th=10 deg. There are 9 frames each of
around 330s duration (from 2143 - 2228). You can clearly see motion in
the tail and material spiraling out from the centre of the coma. The
small black dot at the centre of the coma is the reference pixel for the
filter.

I have done quite a few experiments with this data and I think the
parameters I have chosen are the best compromise to show detail and
motion (i.e. around 300s integrations and L-S with r=2, th=10).

It always amazes me that so much relative motion is visible in active
comets over such a short period of time.

Nick.

On 21/07/2020 12:51, Richard Miles - rmiles.btee at btinternet.com (via
baa-comet list) wrote:
> Thanks Nick.
> I wonder what the rotation period of the nucleus is?
>
> My 10' x 7' close-up image processed first with the Larson-Sekanina
> filter, the second using a rotational gradient filter is here on my BAA
> Members' Page:
> https://britastro.org/node/23409
>
> The frames spanned from 21:50-22:14 UT on 2020 July 20.
>
> Richard
>
> ----- Original Message ----- From: "Nick James" <ndj@nickdjames.com>
> To: <baa-comet@simplelists.com>
> Sent: Tuesday, July 21, 2020 7:11 AM
> Subject: Re: [BAA Comets] NEOWISE close-up
>
>
>> C/2020 F3 (NEOWISE) is now high enough that I can image it using my
>> telescope. I start imaging when the sky is bright since any more than
>> 10s exposure currently saturates the central part of the coma. There
>> is a lot of detail in the inner coma and tail and this is an unsharp
>> masked image of the central 0.5 degree showing streamers in the tail
>> and multiple shells in the coma.
>>
>> http://www.nickdjames.com/Comets/2020/2020f3_20200720_2126_ndj.jpg
>>
>> I remember back in 1997 that Terry Platt produced timelapse movies of
>> the inner coma of C/1995 O1 Hale-Bopp showing the shells spiraling out
>> from the centre. Here are the stills from that movie:
>>
>> https://britastro.org/cometobs/1995o1/1995o1_19970328a_platt.html
>>
>> I also attempted a wide-field image last night using a Sony A7s +
>> Canon 85mm, f/1.2L lens but the light pollution here makes processing
>> it very difficult. It does show the ion tail stretching back to Merak
>> and Dubhe which are the two bright stars in the upper right of this
>> image:
>>
>> http://www.nickdjames.com/Comets/2020/2020f3_20200720_2242_ndj.jpg
>>
>> Nick.
>>
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