This prediction update has been computed by Stephen Kerr based on astrometry from Bill Owen at the Table Mountain Observatory. The TYC position of the target star has been used. This NEW update incorporates two additional asteroid positions (13 December 1999) and as such represents all of the astrometry likely to be available prior to this event. The effect of this update is to move the path slightly to the north (around 0.2 of a path width) with no impact on timing. Given this very small change, the essential details for the event remain unchanged and the text below is not significantly altered from the previous update.

Summary:

The update suggests a shift of about 2 path widths to the south and 150 seconds earlier than that predicted by Goffin. As suggested above, a significant amount of this difference is due to the use of the Tycho Catalogue position of the star instead of the GSC location. The updated path passes just to the south of Adelaide (16:55:00 UTC at very low altitude), just to the north of Melbourne and south of Canberra (16:55:25 UTC). This path also crosses Auckland (16:56:45 UTC) just before local sunrise.

• Date and approx. UT time of event: December 30, 1999 @ 16:56 UT
• Magnitude of target star: 9.0
• Magnitude drop [mag]: 5.4
• Estimated maximum duration [s]: 6.4
• Path description: See above.

• Approximate width [km]: 200 km

• Name: TYC 305 676 = GSC 305 676
• Constellation: Virgo
• J2000 position (TYC Position) [h,m,s; ^o,',"]: 13h 12m 30.9548s; +07^o 01' 12.923"
• Position source: Tycho - Data taken from Guide 7 by Project Pluto.
• V mag [mag]: 9.0
• B-V [mag]: +0.552
• Remarks:
• The target star is in north-eastern Virgo. The star is just over 2 degrees north west of sigma Vir.

• Number, name: (146) Lucina
• Approx. diameter [km]: 137
• Source of used astrometry: Table Mountain Observatory (Bill Owen)
• Number of used observations: 8
• Number of rejected observations: 0
• Time covered by the observations: 1999 12 12 to 1999 12 13

• UT date and time of least geocentric approach: 16:57.6 UTC
• Approx. V mag of minor planet at event [mag]: 13.4
• Geocentric parallax of minor planet ["]: 3.50
• Magnitude drop [mag]: 5.4
• Estimated maximum duration [s]: 6.4
• Apparent motion of minor planet ["/h]: 42.02
• Angular distance to moon, phase of moon [deg,%]: 11, 39%
• Update computed by: Kerr (OCCULT 4.2)

IMPORTANT NOTE!

Astrometric updates such as these should not be taken as definitive, but rather only as an indication of where the true track may lie relative to the original predicted track. Observers must bear in mind that later astrometry, in which the target star is measured in the same field as the asteroid, may still reveal substantial changes to the predicted track and time of the event. For this reason it is most important that observers far from the predicted track still monitor the event.