From djswanastro at outlook.com  Tue Oct 16 08:02:14 2018
From: djswanastro at outlook.com (David Swan)
Date: Tue, 16 Oct 2018 07:02:14 +0000
Subject: [BAA Comets] 46P/Wirtanen
Message-ID: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>

Hello,

It is good to see Martin Mobberley keeping us up to date with 46P while it is still at a very southerly declination.

I have been looking at the University of Maryland's 46P campaign page. There's quite a big difference between the fitted (and extrapolated) light curves generated from COBS observations versus MPC obs. Is this due to the former relating to total VEM and latter false nucleus mag? Or does this to some extent reflect very significant uncertainty on peak brightness around perihelion/perigee?

David Swan

From jdsh at bas.ac.uk  Tue Oct 16 08:31:08 2018
From: jdsh at bas.ac.uk (Shanklin, Jonathan D.)
Date: Tue, 16 Oct 2018 07:31:08 +0000
Subject: [BAA Comets] 46P/Wirtanen
In-Reply-To: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>
References: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>
Message-ID: <LOXP123MB108077CE8B876544248D907683FE0@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>

It is quite important to look at the error bars.  The MPC rarely give any.  I don't give any in the quick look magnitude parameters at https://www.ast.cam.ac.uk/~jds/magpars.htm, but do in the graphs on the visual observations web page and in the papers published in the Journal.  For 46P see https://www.ast.cam.ac.uk/~jds/46p.JPG When I posted this at the beginning of October the error bars were huge, so it is very likely that different groups will come up with different equations.


Regards,

Jonathan Shanklin


________________________________
From: Comets-disc <comets-disc-bounces at lists.britastro.org> on behalf of David Swan <djswanastro at outlook.com>
Sent: 16 October 2018 08:02
To: BAA Comets discussion list
Subject: [BAA Comets] 46P/Wirtanen

Hello,

It is good to see Martin Mobberley keeping us up to date with 46P while it is still at a very southerly declination.

I have been looking at the University of Maryland's 46P campaign page. There's quite a big difference between the fitted (and extrapolated) light curves generated from COBS observations versus MPC obs. Is this due to the former relating to total VEM and latter false nucleus mag? Or does this to some extent reflect very significant uncertainty on peak brightness around perihelion/perigee?

David Swan
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From buczynski8166 at btinternet.com  Tue Oct 16 14:11:24 2018
From: buczynski8166 at btinternet.com (denis buczynski)
Date: Tue, 16 Oct 2018 13:11:24 +0000 (UTC)
Subject: [BAA Comets] 46P/Wirtanen
In-Reply-To: <LOXP123MB108077CE8B876544248D907683FE0@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>
References: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>
 <LOXP123MB108077CE8B876544248D907683FE0@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>
Message-ID: <1299132893.16173654.1539695484345@mail.yahoo.com>

 Perhaps some of the differences are due to the very diffuse nature of this comet. It will be difficult to obtain consistant magnitude estimates as the comet becomes larger and more diffuse in the northern skies.Both visual and comphot magnitude determinations will be affected by the ability to detect of the outer coma in the observations.Conditions such as sky transparency and light pollution will be a limiting factor in dectecting the very outer reaches of the coma.I exepct that imaging wide fields of view using fast short focal length lenses will be needed for the comphot observations. Very low power binoculars and even naked eye (if the comet beomes that bright) will probably be used by the visual observers. From what I have read the coma could become as large as 2 degrees in our skies. It will be another fascinating comet to follow.Denis

    On Tuesday, 16 October 2018, 08:31:31 GMT+1, Shanklin, Jonathan D. <jdsh at bas.ac.uk> wrote:  
 
 
It is quite important to look at the error bars.  The MPC rarely give any.  I don't give any in the quick look magnitude parameters athttps://www.ast.cam.ac.uk/~jds/magpars.htm, but do in the graphs on the visual observations web page and in the papers published in the Journal.  For 46P see https://www.ast.cam.ac.uk/~jds/46p.JPG When I posted this at the beginning of October the error bars were huge, so it is very likely that different groups will come up with different equations.



Regards,

Jonathan Shanklin

From: Comets-disc <comets-disc-bounces at lists.britastro.org> on behalf of David Swan <djswanastro at outlook.com>
Sent: 16 October 2018 08:02
To: BAA Comets discussion list
Subject: [BAA Comets] 46P/Wirtanen Hello,

It is good to see Martin Mobberley keeping us up to date with 46P while it is still at a very southerly declination.

I have been looking at the University of Maryland's 46P campaign page. There's quite a big difference between the fitted (and extrapolated) light curves generated from COBS observations versus MPC obs. Is this due to the former relating to total VEM and latter false nucleus mag? Or does this to some extent reflect very significant uncertainty on peak brightness around perihelion/perigee?

David Swan
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This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system._______________________________________________
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From ndj at nickdjames.com  Tue Oct 16 21:35:21 2018
From: ndj at nickdjames.com (Nick James)
Date: Tue, 16 Oct 2018 21:35:21 +0100
Subject: [BAA Comets] 46P/Wirtanen
In-Reply-To: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>
References: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>
Message-ID: <1b12c781-3526-24d8-6475-4a7e45b5aafc@nickdjames.com>

David,

Magnitudes reported to the MPC are usually a byproduct of people doing 
astrometry and so they tend to use a small, but undefined, photometric 
aperture. They are therefore mostly near to "nuclear" mags. Magnitudes 
on COBS should represent total mags. For a large, extended comet like 
46P the total mag (measured in an aperture of several arcmins) will be 
quite a bit brighter than the nuclear mag (measured in an aperture of a 
few tens of arcsec).

At present visual and CCD observers are getting a total mag of around 10 
with a coma diameter of 10 arcmin or so whereas mags from MPC astrometry 
are much more variable (due to the undefined aperture size) but between 
2 - 4 mags fainter.

The lightcurve here:

http://wirtanen.astro.umd.edu/46P/46P_status.shtml

is the one you are referring to. The MPC mags are not really very useful 
in this case.

Nick.


On 16/10/2018 08:02, David Swan wrote:
> I have been looking at the University of Maryland's 46P campaign page. There's quite a big difference between the fitted (and extrapolated) light curves generated from COBS observations versus MPC obs. Is this due to the former relating to total VEM and latter false nucleus mag? Or does this to some extent reflect very significant uncertainty on peak brightness around perihelion/perigee?


From ndj at nickdjames.com  Tue Oct 16 21:35:21 2018
From: ndj at nickdjames.com (Nick James)
Date: Tue, 16 Oct 2018 21:35:21 +0100
Subject: [BAA Comets] 46P/Wirtanen
In-Reply-To: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>
References: <HE1PR0301MB223616CAC22075CC3B636686A2FE0@HE1PR0301MB2236.eurprd03.prod.outlook.com>
Message-ID: <1b12c781-3526-24d8-6475-4a7e45b5aafc@nickdjames.com>

David,

Magnitudes reported to the MPC are usually a byproduct of people doing 
astrometry and so they tend to use a small, but undefined, photometric 
aperture. They are therefore mostly near to "nuclear" mags. Magnitudes 
on COBS should represent total mags. For a large, extended comet like 
46P the total mag (measured in an aperture of several arcmins) will be 
quite a bit brighter than the nuclear mag (measured in an aperture of a 
few tens of arcsec).

At present visual and CCD observers are getting a total mag of around 10 
with a coma diameter of 10 arcmin or so whereas mags from MPC astrometry 
are much more variable (due to the undefined aperture size) but between 
2 - 4 mags fainter.

The lightcurve here:

http://wirtanen.astro.umd.edu/46P/46P_status.shtml

is the one you are referring to. The MPC mags are not really very useful 
in this case.

Nick.


On 16/10/2018 08:02, David Swan wrote:
> I have been looking at the University of Maryland's 46P campaign page. There's quite a big difference between the fitted (and extrapolated) light curves generated from COBS observations versus MPC obs. Is this due to the former relating to total VEM and latter false nucleus mag? Or does this to some extent reflect very significant uncertainty on peak brightness around perihelion/perigee?


From ndj at nickdjames.com  Fri Oct 26 07:20:04 2018
From: ndj at nickdjames.com (Nick James)
Date: Fri, 26 Oct 2018 07:20:04 +0100
Subject: [BAA Comets] The 2017 Outburst of 174P
Message-ID: <2d02e28e-d682-67ca-a168-1d7b335c7410@nickdjames.com>

I'll be talking about last December's outburst of 174P/Echeclus at the 
BAA AGM next Wednesday in London:

	https://britastro.org/node/11259

This talk will include analysis of the event based on the work of many 
observers who contributed at the time and it is a great demonstration of 
what amateurs can do in this field.

The meeting is open to non-members (although we'd like you to join the 
Association if you can!). If you are able to make it to London please 
come up and say hello. If not, A video of the talk should be on the BAA 
website shortly afterwards although this will only be available to members.

Nick James, Director.


From jdsh at bas.ac.uk  Sun Oct 28 22:19:28 2018
From: jdsh at bas.ac.uk (Shanklin, Jonathan D.)
Date: Sun, 28 Oct 2018 22:19:28 +0000
Subject: [BAA Comets] Visual and equivalent observations
In-Reply-To: <2d02e28e-d682-67ca-a168-1d7b335c7410@nickdjames.com>
References: <2d02e28e-d682-67ca-a168-1d7b335c7410@nickdjames.com>
Message-ID: <LOXP123MB10804187E9D870B8389765E283F20@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>

I'm planning to process the October observations on Tuesday, as I'll be away at the beginning of November.  This includes converting them to TA format for Guy Hurst.  If possible can you send them in before then.


38P is getting to be visible at a more convenient time, particularly now that the clocks have changed to UT in the UK.


Regards,

Jonathan Shanklin
________________________________
This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system.
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From ndj at nickdjames.com  Mon Oct 29 13:05:19 2018
From: ndj at nickdjames.com (Nick James)
Date: Mon, 29 Oct 2018 13:05:19 +0000
Subject: [BAA Comets] Visual and equivalent observations
In-Reply-To: <LOXP123MB10804187E9D870B8389765E283F20@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>
References: <2d02e28e-d682-67ca-a168-1d7b335c7410@nickdjames.com>
 <LOXP123MB10804187E9D870B8389765E283F20@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>
Message-ID: <5db412ed-41f4-5336-5f6e-c8174c23b633@nickdjames.com>

Hi all,

If you submit observations to COBS please make sure that your 
Astronomical Association is set to "British Astronomical Association". 
This allows me to extract your ICQ format observations each month for 
inclusion in our reports.

You can set this on your COBS registration page.

Nick.


On 28/10/2018 22:19, Shanklin, Jonathan D. wrote:
> I'm planning to process the October observations on Tuesday, as I'll be away at the beginning of November.  This includes converting them to TA format for Guy Hurst.  If possible can you send them in before then.
> 
> 
> 38P is getting to be visible at a more convenient time, particularly now that the clocks have changed to UT in the UK.
> 
> 
> Regards,
> 
> Jonathan Shanklin
> ________________________________
> This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system.
> ________________________________
> 
> 
> 
> _______________________________________________
> Comets-disc mailing list
> Comets-disc at lists.britastro.org
> http://lists.britastro.org/mailman/listinfo/comets-disc
> 


From jdsh at bas.ac.uk  Wed Oct 31 21:33:46 2018
From: jdsh at bas.ac.uk (Shanklin, Jonathan D.)
Date: Wed, 31 Oct 2018 21:33:46 +0000
Subject: [BAA Comets] Visual update
In-Reply-To: <LOXP123MB10804187E9D870B8389765E283F20@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>
References: <2d02e28e-d682-67ca-a168-1d7b335c7410@nickdjames.com>,
 <LOXP123MB10804187E9D870B8389765E283F20@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>
Message-ID: <LOXP123MB1080493B94AD53BDC1D7FE5B83CD0@LOXP123MB1080.GBRP123.PROD.OUTLOOK.COM>

I've now processed all the visual and VEM observations and updated the visual web page https://www.ast.cam.ac.uk/~jds/.  Nick James kindly extracted BAA observations from COBS, but it is still helpful for observers to send observations direct to me, ideally towards the end of the month.


The main conclusions are that 38P is probably near its peak brightness, and that 46P is on track to reach naked eye brightness around the time of its close approach.  It will be quite large, so naked eye may well be the best way to see it.  It is currently too far south for UK observers, but will soon be heading north, and should get sufficiently above the horizon in late November


Regards,

Jonathan Shanklin


________________________________
This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system.
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