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(meteorobs) Comet Tilbrook

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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