Just to let everyone know - I download all registered BAA observations from COBS on a monthly basis, usually on the 3rd of the month, but occasionally earlier or later.  The timing is so that I can process the observations and format them for publication in The Astronomer, which has a deadline at the start of the month.  I download approximately 45 days worth of observations, so slightly late submissions won't be missed.  When I come to analyse periodic comets for the Journal papers I download all available observations for those periodic comets with five or more observed returns.

To answer Ronan's question - I think the enhancement would have to be around two magnitudes to make it readily observable in the evening twilight on December 9 and 10.  If it was three magnitudes then December 5 to 12 becomes possible.  In the unlikely event of four magnitudes, then from now (assuming it suddenly gets much brighter) until December 13.  Throughout this period the best window for seeing it is in the morning sky, with the sky beginning to get bright at 06:20 now and 06:30 by December 13 (for southern England).

Regards,

Jonathan Shanklin
BAA Comet Section visual observations co-ordinator
https://www.ast.cam.ac.uk/~jds/

-----Original Message-----
From: baa-comet@simplelists.com <baa-comet@simplelists.com> On Behalf Of Nick James
Sent: 02 December 2021 10:35
To: baa-comet@simplelists.com
Subject: Re: [BAA Comets] 2021 A1 (Leonard)

Morning Jonathan/all,

It was a frustrating morning here with lots of fast moving cloud and only a few short gaps. My best images were taken at around 04:00. I get a total magnitude of 6.9 using comphot on the green pixels of my ASI294 referenced to Gaia DR2. The coma diameter is almost 16 arcmin and the tail is visible on my image to around 1.5 deg. The image is here:

https://britastro.org/observations/observation.php?id=20211202_102625_1e4f221e76bcaf54

On the morning of November 29 I got 7.2 using comphot and the same equipment. Thomas Lehmann kindly did a reduction of my images using AIRTOOLS and got 7.13 (ref APASS) and 7.24 (ref Gaia EDR3) so both software approaches a producing the same results.

There are quite a few BAA estimates on COBS. Do you want me to download those for use in your analysis or will you do that?

I also have images with the HD11/IMX455 which I haven't processed yet but they show a nice, compact pseudo-nucleus so no signs of anything bad happening to this comet.

Nick.

On 02/12/2021 08:15, Jonathan Shanklin - BAS wrote:
> I observed the comet this morning from central Cambridge.  It was worth getting up early for.  The comet was mag 6.7 in 20x80B at 06:19, with a tail ¾ of a degree long.  It would probably have been more impressive from a dark sky location.
>
> This is about a magnitude fainter than predicted by the magnitude analysis that I ran last month, but within the error bars.  I’ll be updating the analysis later today or tomorrow.  It could brighten by another couple of magnitudes before UK observers lose it around December 11.
>
> Regards,
>
> Jonathan Shanklin
> BAA Comet Section visual observations co-ordinator
> https://www.ast.cam.ac.uk/~jds/
>
>
>
>
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