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(meteorobs) Re: Comet Tilbrook

John,

Your data on Comet Tilbrook is interesting. For years I have seen low,
but noticeable activity from Ursa Major during the Geminids. I have
never really pursued this activity but one of these year's I'll try
plotting these critters just to see if I come up with a radiant.

Clear Skies!

Bob Lunsford



JG wrote:
> 
> Good luck to A Jure on his exams etc....
> 
> I'll mention Tilbrook's comet, if somebody kindly forwards me the
> guesstimated RA, Dec, Vgeo and max date [and date range & ZHR ] of the xi
> Bootids as currently best known, and possibly also the same details for the
> xi Draconids... ...just when you thought it was safe to assume you'd got a
> complete list of meteor showers...
> 
> Posting to meteorobs will suffice, as I monitor the archives list.
> 
> Anyway, Tilbrook: basically I'd found a few radar meteors that appeared
> co-orbital in a general test I did of many comet orbits against many meteor
> orbits.  At the time I had a bit of bother with this, as the only source
> reference I had for Drummond's D' criterion had one itsy bitsy typo in it!
> This only caused problems _sometimes_, when special circumstances occured,
> but not being a maths whiz either, I couldn't figure out where the problem
> was, until I finally found a better article with the same equations in it,
> this time _without_ typos!  Anyway, only Tilbrook 1999 A1 came up for a
> recent object with *unknown* shower.
> 
> C/1999 A1 Tilbrook gives rough radiant details of RA 165 deg, Dec +60 deg,
> Vgeo 50 km/s, max 11/12th of Dec 1999.  The comet hit perihelion almost a
> year earlier in late Jan '99, which was one reason I didn't worry about it
> too much.  We're talking a radiant that'd lie half way twixt alpha and beta
> UMa.  There were about half a dozen radar meteors, and one Dutch DMS video
> meteor with very similar orbits.  However, half a dozen radar meteors out
> of 63,000 isn't many, and that time of year is usually well covered, so
> you'd expect more if real.  In comparison, I only found 1 radar meteor
> matching the orbit of 1999 J3 LINEAR.
> 
> Cos nobody saw any, I reckon they don't exist... ...maybes.  I kept quiet
> about it at the time cos I was exceptionally new to this type of work and
> ideas, and whilst I was thinking about it, the November Linearids thing
> came up, and saying anything seemed a bit bandwagonny...
> 
> Now, if anybody is really interested in this sort of thing, go to
> www.dmsweb.org and select the link to the journal Radiant in the sidebar
> menu.  Then follow the "previous" issue link to get a paper called
> DMSorbits or similar.  Then the "current" issue link to find one called
> DMSdcrit or similar. They're in English and AcroRead PDF format.
> 
> Note that the first paper was written when the author had barely studied
> this subject, and some of the stuff in the DMSorbit article is almost
> embarrassingly niaive.  Thus DMSdcrit was a re-write of that paper to make
> up for that fact, though that too has probably got the odd mistake/niaive
> assumption here and there.
> 
> At least the articles are a source of top quality references.
> 
> And as to how anybody is ever going to be able to distinguish any Sekiids,
> even if they do exist, I dunno!
> 
> Finally, Bob Lunsford is right.  Multistation video surveys in the US would
> not only be useful re cloud over Europe, but would also beautifully fill
> the timezone gap between the Dutch DMS team and the Japanese MSSWG team.
> Why multistation?  Cos that way you can get orbits [double station will
> usually suffice].  The IMO webpages carry a lot of freeware for the
> processing of this sort of data, although I have absolutely no idea whether
> it can cope with the different vid standards the US has compared to Europe.
>  Papers on the topic may well be accessible via www.dmsweb.org.  But don't
> ask me, it's all at a "I know _of_ it" level as far as I'm concerned :)
> 
> Cheers
> 
> John
> 
> John Greaves
> UK
> 
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