This prediction update has been computed by Steve Preston of the Medina, Washington (state) in the United States based on astrometry from Ron Stone of the US Naval Observatory - Flagstaff Station supplemented with data from the AstDys database. The UCAC position of the target star has been used.

Summary:

This updated path lies around 3 path widths to the north of that given by Edwin Goffin and around 1 minute ealier. The path clips the tip of Fraser Island and would include Bundaberg at 8:19:30 UT. Running west, the path quickly emerges into the twilight and daylight parts of western Queensland, the Northern Territory and Western Australia.

The uncertainty of this calculation is quite large and Brisbane based observers lie well within the error tollerance with the most probable time of 8:19 UT.

Potential observers on the eastern coast of Australia are urged to practice the location of this field on previous nights as there will be little time available between the event and the onset of sufficient darkness to allow observation.

THE EVENT AT ONE GLIMPSE:

• Date and approx. UT time of event: July 22, 2001 @ 8:19 UT
• Magnitude of target star: 10.44
• Magnitude drop [mag]: 6.6
• Estimated maximum duration [s]: 8.1
• Path description: See above.
• Goffin's original chart reference: A01_0731

• Approximate width [km]: 45
• Uncertainty [path widths]: 3.1 (one sigma)
• Map: See below
• Circles along the path are OCCULT calculated exact centerline points !!!!

• Name: TYC 6224-00565-1 = PPM 265716
• Constellation: Ophiuchus
• J2000 position [h,m,s; ^o,',"]: 16h 36m 34.5367s; -20^o 25' 54.381"
• Position source: UCAC
• V mag [mag]: 10.44
• B-V [mag]: +1.31
• Remarks:
• The target star is in southwestern Ophiuchus. It lies approximately 1.5 degrees northeast of omega Ophiuchi (magnitude = 4.4) and 6.25 degrees north-northeast of Antares (alpha Scorpii - magnitude = 1.1).

• Number, name: (515) Athalia
• Approx. diameter [km]: 43.0
• Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), AstDys
• Number of used observations: 322
• Number of rejected observations: 26
• Time covered by the observations: 1903 09 20 - 2001 06 22
• Residuals ["] (RA,DE): 0.055", 0.053" (1 sigma)

• UT date and time of least geocentric approach: 2001 July 22, 8:09.6 UT
• Approx. V mag of minor planet at event [mag]: 17.0
• Geocentric parallax of minor planet ["]: 3.10
• Magnitude drop [mag]: 6.6
• Estimated maximum duration [s]: 8.1
• Apparent motion of minor planet ["/h]: 9.24
• Angular distance to moon, phase of moon [deg,%]: 109, 4%
• Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit).

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.