This prediction update has been computed by Jan Manek based on astrometry from USNO/Flagstaff and Table Mountain Observatory. The Hipparcos position of the star has been used.

Summary:

This calculation gives only a small ~0.3 path width NE shift with the occultation time ~0.3 minutes later compared to Edwin Goffin's nominal prediction.

The path for this event runs over N Iran, the middle of Afghanistan and Pakistan at ~20:27 UT, north India and south Nepal at ~20:28.5 UT, Bangladesh, Burma at ~20:30 UT, Thailand at ~20:31 UT, Kampuchea, South Vietnam at ~20:32 UT, then over NE Borneo with Brunei at ~20:34 UT and the Celebes at ~20:35 UT. Finally the path runs over Arnhem Land in Australia's Northern Territory, with Darwin just south of the path at ~20:37 UT.

Note that eastern sites will be in daylight at event time!

THE EVENT AT ONE GLIMPSE:

• Date and approx. UT time of event: September 6, 1999 @ 20:29 UT (India) and 20:37 UT (Australia)
• Magnitude of target star: 8.1
• Magnitude drop [mag]: 3.8
• Estimated maximum duration [s]: 14.0
• Path description: See above.

• Approximate width [km]: 180
• Uncertainty [path widths]: 0.8
• Uncertainty in time [s]: 15
• Map: See below
• Remarks: Uncertainities are given on the basis of the nominal star position errors and the expected asteroid positional accuracy.
• Circles along the path are OCCULT calculated exact centerline points.

• Name: HIP 18028 = SAO 111463 = PPM 146973 = GSC 0066.0143
• Constellation: Taurus
• J2000 position [h,m,s; ^o,',"]: 03h 51m 10.288s; +00^o 56' 00.81"
• Position source: Hipparcos
• Estimated accuracy ["]: 0.02" (0.01", 0.01")
• V mag [mag]: 8.11
• B-V [mag]: +0.33
• Remarks:
  1. The target star is in SW Taurus, close to the border with Eridanus, quite far from any bright familiar stars in a poor region. Some 38' north of the target is mag 6.6 SAO 111453 and 7' NW of the target is mag 9.4 SAO 111458 (this star was occulted 12 hours earlier for observers in USA).

• Number, name: (194) Prokne
• Approx. diameter [km]: 174
• Source of used astrometry: USN0/Flagstaff (Ron Stone) + TMO (Bill Owen)
• Number of used observations: 12 USNO + 10 TMO
• Number of rejected observations: 1 USNO + 1 TMO
• Time covered by the observations: 1998 02 26 - 1999 08 23
• RMS residuals ["] (RA,DE): 0.07", 0.05"
• Estimated positional accuracy at epoch of event ["]: 0.09"
• Remarks: No 'mean' positions were used, only the original ones.

• UT date and time of least geocentric approach: 20:34:56 UT
• Approx. V mag of minor planet at event [mag]: 11.9
• Geocentric parallax of minor planet ["]: 4.971
• Magnitude drop [mag]: 3.8
• Estimated maximum duration [s]: 14.0
• Apparent motion of minor planet ["/h]: 35.05
• Angular distance to moon, phase of moon [deg,%]: 70, 11%
• Update computed by: Manek

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.