[BAA Comets] Science from visual observationsof 29P/Schwassmann-Wachmann: a plea

[Richard Miles]

Excellent Jonathan - Thank you for your feedback.

I have trawled thgrough a lot of visual data (e.g. from COBS and some from 
the MPC/CB) and was unable to find much additional information, over and 
above that gleaned from CCD observations (since 2002 August), to better 
define the shape of 29P's complex lightcurve, the time of an outburst, or 
indeed identify a new outburst that would otherwise have been missed.

Earlier visual data, prior to 2002, are more useful as there were few CCD 
measures in those days and they were mainly Total Magnitude ones. 
Photography pre-2002 also helps of course.

The question is, "Can visual observers do better in the future by adopting a 
specific methodology for this comet?"

I am very much open to suggestions and have an open mind as to how a visual 
observer might do this.

I should add that this is all part of a pre-amble to putting together a 
BAA-led observing campaign on 29P due to start in 2017 March. This is a very 
good time to get our ducks in line, since the comet will be favourably 
placed for observation for the next decade or so.

Clear skies,
Richard Miles


----- Original Message ----- 
From: "Shanklin, Jonathan D." <jdsh at bas.ac.uk>
To: "BAA Comets discussion list" <comets-disc at lists.britastro.org>
Sent: Saturday, December 10, 2016 7:39 PM
Subject: Re: [BAA Comets] Science from visual observationsof 
29P/Schwassmann-Wachmann: a plea


> There are a few "I" estimates of the comet in the files, and these are 
> mostly immediately after an outburst has commenced, with the comet at DC=8 
> or 9.  Once the coma becomes diffuse the visual nuclear magnitude is 
> likely to become too dependent on observing conditions to be of much 
> systematic use.  This is one reason why visual nuclear magnitudes are not 
> normally reported, and also why many reported m2 magnitudes are highly 
> discordant.
>
>
> You might be able to use some combination of the reported visual 
> magnitude, coma diameter and DC to help constrain things, but my opinion 
> is that using visual magnitudes is unlikely to put much of a constraint on 
> the time of outburst.  Of course presence / absence observations do place 
> some constraint.
>
>
> I think that for the study you are suggesting it would be best to use 
> electronic observations from telescopes in sites with conditions of good 
> seeing and transparency.
>
>
> Regards,
>
> Jonathan Shanklin
>
>
> ________________________________
> From: Comets-disc <comets-disc-bounces at lists.britastro.org> on behalf of 
> Richard Miles <rmiles.btee at btinternet.com>
> Sent: 10 December 2016 15:51
> To: asvcometsection at yahoogroups.com; BAA Comets discussion list; 
> comets-ml at yahoogroups.com
> Subject: [BAA Comets] Science from visual observations of 
> 29P/Schwassmann-Wachmann: a plea
>
> <<Many visual observers subscribe to these mailing groups hence I am 
> sending
> a request aimed primarily at them concerning future visual observation of
> 29P/SW1>>
>
>
> The tradition for the visual observer is to estimate the Total Magnitude
> (m1) and to express this in effect as a V magnitude. That is fine and 
> dandy
> for virtually all fainter comets which do not exhibit a greatly extended
> tail. But of all the comets we know, 29P/SW1 is the exception to the rule
> and I think we need to re-examine how the comet should be observed.
>
> Recent studies have shown that the large majority of dust and debris in 
> its
> coma arrives there through episodic outbursts. The duration of each 
> outburst
> is very short in that most (>95%) rise to full brightness in 1-2 hours; 
> the
> source of the outburst having effectively shut down early on in the
> process.**
>
> When studying 29P/SW1, amongst others, two pieces of information of value 
> to
> science are; (a) the time of each outburst, and (b) the brightness of the
> pseudonucleus (i.e. the immediate region close to the actual nucleus). So 
> to
> maximise the scientific value of the observations, visual workers should
> consider submitting TWO reports: one of the Total Magnitude and a second 
> one
> giving the Nuclear Magnitude (m2). Clearly, whilst the normal observing
> methodologies for an extended source are suitable for the former, a method
> akin to variable star observation would seem more applicable when 
> estimating
> the latter.
>
> ***I would be grateful for any feedback from visual observers as to how 
> they
> might go about elaborating their observing methodology specifically for
> 29P/SW1.***
>
> I should add that although the comet has been a difficult target tracking
> through the southern Milky Way during the last few years and is now 
> reaching
> the end of its current apparition (solar elongation ~37 deg and 
> decreasing),
> from next year until the end of 2020 it will lie within 16 degrees of the
> celestial equator where it will be easily observable from both northern 
> and
> southern hemispheres. 2017 will therefore be a good time to adopt an
> enhanced observing methodology for this comet to maximise the science 
> yield.
> It would be good therefore if some mutually agreed approach to Nuclear
> Magnitude estimation could be arrived at in the near future to be adopted 
> by
> visual workers.
>
> Thanks in advance.
>
> Richard Miles
> British Astronomical Association
>
>
>
> ** P.S - Given this scenario, the use of the Afrho parameter to describe 
> the
> activity of 29P/SW1 is only a proxy parameter for dust production since
> A'Hearn's model is based on continual supply of dust to the coma; for
> instance, it is often equated to dust production rate expressed as kg/s.
> This topic could be another discussion thread ...
>
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