Nick,

The lightcurve you have so far from all the contributors of 12P is impressive.

Eliot Herman has a an almost nightly sequence of Luminance images from Utah (0.43-m iTel T19 scope).
Our standard photometry has been G mags but with a much smaller measuring aperture of 3.5" radius.

Last night's imaging with T19  shows a 0.27 mag drop in brightness compared to 24 hours earlier, which I am now interpreting as a mini-outburst on December 28 !
(N.B. The comet did pass a field star at the time and later images were affected by cloud so if I were to use a 9" radius aperture)

From the BAA data so far it is clear that the last 3 strong outbursts have decreased stepwise in brightness from the most intense one (of all) of November 14.
So although I said that December 29.1 was the nominal date for another outburst, I have warned that we may have to look carefully given that these events have been weakening of late.

I shall finish the 3.5" radius photometry and next select images to perform the 9" radius G photometry for inclusion in the BAA lightcurve.
Here are the last 3 nights' data:

0012P         C2023 12 27.08315 19 23 29.44 +37 44 25.9          14.51G      U94 3.15" (3.56") 60s Lum Herman
0012P         C2023 12 27.08407 19 23 29.56 +37 44 25.0          14.50G      U94
0012P         C2023 12 27.08499 19 23 29.66 +37 44 26.2          14.51G      U94
0012P         C2023 12 27.08590 19 23 29.83 +37 44 26.1          14.52G      U94
0012P         C2023 12 27.08681 19 23 29.99 +37 44 24.9          14.48G      U94
0012P         C2023 12 27.08771 19 23 30.10 +37 44 25.5          14.50G      U94
0012P         C2023 12 27.08862 19 23 30.20 +37 44 25.3          14.54G      U94
0012P         C2023 12 27.08953 19 23 30.36 +37 44 25.8          14.54G      U94
0012P         C2023 12 27.09044 19 23 30.55 +37 44 25.3          14.42G      U94
0012P         C2023 12 27.09134 19 23 30.70 +37 44 26.0          14.52G      U94
0012P         C2023 12 27.09225 19 23 30.78 +37 44 24.7          14.60G      U94
0012P         C2023 12 27.09316 19 23 30.88 +37 44 25.7          14.55G      U94
0012P         C2023 12 27.09406 19 23 31.13 +37 44 25.7          14.53G      U94
0012P         C2023 12 27.09497 19 23 31.18 +37 44 25.8          14.59G      U94
0012P         C2023 12 27.09588 19 23 31.40 +37 44 25.1          14.59G      U94
0012P         C2023 12 27.09678 19 23 31.50 +37 44 25.3          14.53G      U94
0012P         C2023 12 27.09770 19 23 31.61 +37 44 26.1          14.49G      U94 star
0012P         C2023 12 27.09861 19 23 31.79 +37 44 25.3          14.38G      U94 star

**Outburst at 2023 12 28.1 ± 0.4  14.54G => 14.30G  Amplitude 0.24 mag

0012P         C2023 12 29.08829 19 28 46.63 +37 44 12.4          14.32G      U94 3.15" (3.56") 60s Lum Herman
0012P         C2023 12 29.08919 19 28 46.76 +37 44 13.1          14.35G      U94
0012P         C2023 12 29.09009 19 28 46.90 +37 44 12.5          14.33G      U94
0012P         C2023 12 29.09100 19 28 47.07 +37 44 13.0          14.36G      U94
0012P         C2023 12 29.09190 19 28 47.22 +37 44 12.2          14.30G      U94
0012P         C2023 12 29.09280 19 28 47.32 +37 44 12.5          14.30G      U94
0012P         C2023 12 29.09372 19 28 47.54 +37 44 12.5          14.33G      U94
0012P         C2023 12 29.09462 19 28 47.64 +37 44 12.5          14.26G      U94
0012P         C2023 12 29.09552 19 28 47.78 +37 44 12.4          14.27G      U94
0012P         C2023 12 29.09642 19 28 47.90 +37 44 12.7          14.26G      U94
0012P         C2023 12 29.09734 19 28 48.03 +37 44 12.1          14.29G      U94
0012P         C2023 12 29.09824 19 28 48.18 +37 44 12.5          14.32G      U94
0012P         C2023 12 29.09916 19 28 48.34 +37 44 12.4          14.27G      U94
0012P         C2023 12 29.10006 19 28 48.53 +37 44 12.6          14.31G      U94
0012P         C2023 12 29.10097 19 28 48.65 +37 44 12.2          14.28G      U94
0012P         C2023 12 29.10188 19 28 48.78 +37 44 12.5          14.30G      U94
0012P         C2023 12 29.10279 19 28 48.91 +37 44 11.8          14.35G      U94
0012P         C2023 12 29.10370 19 28 49.08 +37 44 12.0          14.31G      U94
0012P         C2023 12 29.10461 19 28 49.17 +37 44 11.7          14.32G      U94
0012P         C2023 12 29.10551 19 28 49.34 +37 44 12.4          14.29G      U94

0012P         C2023 12 30.08947 19 31 28.15 +37 44 17.4          14.53G      U94 3.15" (3.56") 60s Lum Herman
0012P         C2023 12 30.09037 19 31 28.30 +37 44 17.5          14.52G      U94
0012P         C2023 12 30.09388 19 31 28.88 +37 44 17.5          14.59G      U94
0012P         C2023 12 30.09479 19 31 29.03 +37 44 17.7          14.62G      U94
0012P         C2023 12 30.09569 19 31 29.19 +37 44 17.0          14.56G      U94
0012P         C2023 12 30.09660 19 31 29.29 +37 44 17.3          14.55G      U94 star
0012P         C2023 12 30.09751 19 31 29.45 +37 44 17.5          14.48G      U94 star
0012P         C2023 12 30.09843 19 31 29.62 +37 44 17.3          14.59G      U94
0012P         C2023 12 30.09933 19 31 29.76 +37 44 17.0          14.61G      U94

Richard

-----Original Message-----
From: baa-comet@simplelists.com <baa-comet@simplelists.com> On Behalf Of Nick James
Sent: Saturday, December 30, 2023 9:43 AM
To: baa-comet@simplelists.com
Subject: Re: [BAA Comets] 12P/Pons-Brooks outburst due?

Further to my note of three days ago there is no sign of any signifiant outburst yet. The latest data I have is for Dec 30.07. The recent scatter may be real or it may be due to the different systems being used.

If you do manage to get any 9 arcsec photometry despite the current really bad weather please send it to me.

Nick.

On 27/12/2023 13:13, Nick James wrote:
> Hi all,
>
> It is coming up to 15 days since the last 12P outburst which took
> place sometime around December 14.5. The last few outbursts have been
> on a 15 day cadence and so we might be coming up to another one.
> Richard Miles is developing a detailed theory which explains the
> outbursts and the shape of the post-outburst inner coma and
> observations around the time of the outbursts are particularly important.
>
> The weather in southern England has been particularly dull over the
> Christmas period but I've been monitoring the comet using the Alnitak
> CDK 17 in Spain although the weather there has not been particularly
> good either and the Moon has been a problem too. My latest
> measurements from last night using very poor images showed a magnitude
> of around 13.2. Denis Buczynski got similar from his observatory in NE Scotland.
> The attached plot shows the latest observations.
>
> If you have any photometry that you have not yet submitted please send
> it to me. For this lightcurve I need unfiltered or V vs Gaia G
> measured in an approximately 9 arcsec radius aperture. This is our
> standard setup for astrometry using Astrometrica and so you just need
> to send me the photometry report that gets generated at the same time as the astrometry.
>
> Please keep observing this object as frequently as possible so that we
> can pick up the next outburst as it happens.
>
> Thanks,
>
> Nick.
> To unsubscribe from this list please go to
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> 2vuAnC

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