This prediction update is supplied by Jan Manek of the Stefanik Observatory, Prague, and is based on USNO/Flagstaff astrometry for the minor planet and the TAC star position.

Summary:

This calculation gives ~0.7" south shift and time ~3 seconds later compared to Goffin's nominal path.

THE EVENT AT ONE GLIMPSE:

• Date and approx. UT time of event: December 7, 1999 @ 18:08 UT
• Magnitude of target star: 11.3 as per TAC. Visual estimate 11.6.
• Magnitude drop [mag]: 1.3 as per TAC. Visual estimate 1.0
• Estimated maximum duration [s]: 13.8
• Path description: Far south coast of New South Wales and southern Victoria. Note that there is a significant amount of error in this predicted path.

• Approximate width [km]: 240
• Uncertainty [path widths]: 2.5
• Uncertainty in time [s]: 30
• Map: See below
• Remarks:Uncertainties are given on basis of nominal errors of observations.
• Circles along the path are OCCULT calculated exact centerline points.

• Name: TAC +04^o03607 = GSC 125 262
• Constellation: Orion
• J2000 position [h,m,s; o,',"]: 5h 56m 00.666s; +04^o 41' 17.88"
• Position source: TAC 1.0
• Estimated accuracy ["]: 0.3" (0.2", 0.2")
• V mag [mag]: 11.34
• B-V [mag]: +0.7
• Remarks: Target star is a TAC star. It is the main source of path uncertainty. V mag is also uncertain. Visual estimate = 11.6.
• Target star is in north-eastern Orion, around 2.7 degrees south of Betelgeuse. Target star is 4.2' south of 9.7 mag star SAO 113274.

• Number, name: (238) Hypatia
• Approx. diameter [km]: 156.0 km
• Orbit source: calculation Manek
• Source of used astrometry: USNO/Flagstaff (Ron Stone), TMO (Bill Owen)
• Number of used observations:39 USNO, 5 TMO
• Number of rejected observations: 1 USNO (1998 09 18.238925)
• Time covered by the observations: 1998 07 02 - 1999 11 30
• Rms residuals ["] (RA,DE): 0.05", 0.05"
• Estimated positional accuracy at epoch of event ["]: 0.05"
• Remarks: (Note by J. Manek) The rejection of 1 USNO position is more a 'cosmetic' intervention than a must. The observations are perfect.

• UT date and time of least geocentric approach: 18:11:33 UT
• Approx. V mag of minor planet at event [mag]: 12.2
• Geocentric parallax of minor planet ["]: 4.888
• Magnitude drop [mag]: 1.3 ?? (See notes above)
• Estimated maximum duration [s]: 13.8
• Apparent motion of minor planet ["/h]: 31.28
• Angular distance to moon, phase of moon [deg,%]: 158, 0%

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.