This prediction update has been computed by Graham Blow based on 8 astrometric positions from Alex Liu in Exmouth, WA. The ACT position of the star has been used.

Summary:

The updated track crosses north-central Australia, from the base of Cape York to Exmouth, WA.

Event time is in accord with the Goffin prediction and about 30 seconds earlier than the nominal OCCULT prediction. (Updated time is about 14h 10.5m for Exmouth).

THE EVENT AT ONE GLIMPSE:

• Date and approx. UT time of event: July 20, 1999 @ 14:09 UT
• Magnitude of target star: 9.89
• Magnitude drop [mag]: 2.9
• Estimated maximum duration [s]: 5.9
• Path description: North-central Australia

• Name: TYC 6857 00875
• J2000 position [h,m,s; o,',"]: 18h 31m 33.304s; -24^o 09' 48.44"
• Position source: ACT
• V mag [mag]: 9.89

• Number, name: (261) Prymno
• Approx. diameter [km]: 53
• Source of used astrometry: Liu
• Number of used observations: 8
• Number of rejected observations: 0
• Time covered by the observations: 1999 07 19

• UT date and time of least geocentric approach: 14:09 UT
• Approx. V mag of minor planet at event [mag]: 12.74
• Geocentric parallax of minor planet ["]: 6.048
• Magnitude drop [mag]: 2.9
• Estimated maximum duration [s]: 5.9
• Apparent motion of minor planet ["/h]: 30.43
• Angular distance to moon, phase of moon [deg,%]: 68, 52%

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.