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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.</div><div>Denis<br></div><div><br></div>
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On Tuesday, 16 October 2018, 08:31:31 GMT+1, Shanklin, Jonathan D. <jdsh@bas.ac.uk> wrote:
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<p style="margin-top:0;margin-bottom:0;">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
<a shape="rect" class="ydp1e7ea616yiv6074140236OWAAutoLink" href="https://www.ast.cam.ac.uk/~jds/magpars.htm" rel="nofollow" target="_blank">https://www.ast.cam.ac.uk/~jds/magpars.htm</a>, but do in the graphs on the visual observations web page and in the papers published in the Journal. For 46P see <a shape="rect" class="ydp1e7ea616yiv6074140236OWAAutoLink" href="https://www.ast.cam.ac.uk/~jds/46p.JPG" rel="nofollow" target="_blank">https://www.ast.cam.ac.uk/~jds/46p.JPG</a> 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.</p>
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</font><div class="ydp1e7ea616yiv6074140236PlainText">Regards,<br clear="none">
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Jonathan Shanklin</div>
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<div dir="ltr" id="ydp1e7ea616yiv6074140236divRplyFwdMsg"><font style="font-size:11pt;" face="Calibri, sans-serif" color="#000000"><b>From:</b> Comets-disc <comets-disc-bounces@lists.britastro.org> on behalf of David Swan <djswanastro@outlook.com><br clear="none">
<b>Sent:</b> 16 October 2018 08:02<br clear="none">
<b>To:</b> BAA Comets discussion list<br clear="none">
<b>Subject:</b> [BAA Comets] 46P/Wirtanen</font>
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</span></font><div class="ydp1e7ea616yiv6074140236PlainText">Hello,<br clear="none">
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It is good to see Martin Mobberley keeping us up to date with 46P while it is still at a very southerly declination.<br clear="none">
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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?<br clear="none">
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David Swan<br clear="none">
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