This prediction update is supplied by Jan Manek of the Stefanik Observatory, Prague, and is based on Table Mountain astrometry for the minor planet and the TRC star position.

Summary:

The astrometry indicates a VERY SIGNIFICANT path shift of a full 2" to the south, with a time ~3 minutes later, compared to Edwin Goffin's nominal prediction. This is because a rather old orbit was used for the nominal prediction together with the TYCHO star position. Large corrections derived from the TMO astrometry together with the new TRC1.0 position of the star are responsible for the shift.

The resulting track runs almost entirely over the southern ocean, with only the very south of South America in the path. There is no chance that New Zealand or Australian observers will see the event.

THE EVENT AT ONE GLIMPSE:

• Date and approx. UT time of event: June 5, 1999 @ 09:50 UT
• Magnitude of target star: 10.4
• Magnitude drop [mag]: 2.4
• Estimated maximum duration [s]: 11.7
• Path description: The path runs almost entirely over the southern ocean, and across the very south of South America. There is no chance for New Zealand or Australian observers.

• Approximate width [km]: 180
• Uncertainty [path widths]: 1.2
• Uncertainty in time [s]: 20
• Map: See below
• Remarks: Uncertainities are given on the basis of the nominal errors in the observations.
• Circles along the path are OCCULT calculated exact centerline points.

• Name: TYC 6786 01029 1
• Constellation: Scorpius
• J2000 position [h,m,s; o,',"]: 15h 54m 10.083s; -27o 45' 51.33"
• Position source: TRC 1.0
• Estimated accuracy ["]: 0.07" (0.06", 0.04")
• V mag [mag]: 10.43
• B-V [mag]: +0.62
• Remarks:
  1. TYCHO gives quality flag 4 (high) and no duplicity flag.
  2. The target star is 26' south of the mag 6.2 star SAO 183907. This is in western Scorpius, about 1.6 degrees NW of the mag 3.9 star rho Sco or 2 degrees SW of the mag 2.9 star pi Sco.

• Number, name: (508) Princetonia
• Approx. diameter [km]: 147
• Orbit source: calculation Manek
• Source of used astrometry: Table Mountain Observatory (Bill Owen)
• Number of used observations: 5 TMO
• Number of rejected observations: 0
• Time covered by the observations: 1999 05 27 - 1999 05 31
• Rms residuals ["] (RA,DE): 0.07", 0.08"
• Estimated positional accuracy at epoch of event ["]: 0.08"

• UT date and time of least geocentric approach: 09:45:35 UT
• Approx. V mag of minor planet at event [mag]: 12.7
• Geocentric parallax of minor planet ["]: 4.164
• Magnitude drop [mag]: 2.4
• Estimated maximum duration [s]: 11.7
• Apparent motion of minor planet ["/h]: 29.47
• Angular distance to moon, phase of moon [deg,%]: 80, 69%

This prediction update has been computed by Graham Blow based upon two astrometric positions of the minor planet obtained at Table Mountain Observatory on May 27. The ACT position of the star has been used.

Path Update:

• The updated path lies ~0.4 arcsec south of the OCCULT prediction, and south of Tasmania and New Zealand. The track crosses Western Australia in the vicinity of Perth, but at low altitude.
• Predicted event times are about 1.5 minutes later than Goffin's prediction. Approximate times are 09h 51m for Victoria/SA and 09h 52.5m for WA.

IMPORTANT NOTE!

• The error bars on the update are quite large.
• Check the website again as this prediction may change.

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.