RASNZ Occultation Section - Eva Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (164) EVA - 2000 JUNE 17

THIS UPDATE REPLACES THE PREVIOUS UPDATE OF 12 JUNE.

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

[Detailed finder chart by Jan Manek]

Goffin's path crosses the North Island of New Zealand around Auckland running south-west across the Tasman Sea passing just to the south of Tasmania. The path given by OCCULT lies around 0.6" to the south-east and 40 seconds later. It clips the South Island of New Zealand from Dunedin to Invercargill including Stewart Island.

UPDATE: 13 June 2000

This prediction update has been computed by Jan Manek of Stefanik Observatory based on astrometry from Ron Stone of the US Naval Observatory - Flagstaff Station. The Hipparcos position of the target star has been used.

Summary:

This update places the new path 6 path widths to the south-east of that given by Edwin Goffin and around 30 seconds later. This new path crosses the South Island of New Zealand from the north-east. Christchurch (11:56:50 UT), Timaru and Queenstown (11:57:15 UT) lie within the updated path, while Napier, Wellington (11:56:30 UT), Dunedin and Invercargill (11:57:20 UT) all lie within the error bounds of the calculation.

While the presence of the near full moon only 15 degrees from the field will complicate the observation, the brightness of the target star and the ready supply of bright neighbouring star should allow easy navigation and observing. What better way to spend a Saturday night !!!

THE EVENT AT ONE GLIMPSE:

Date and approx. UT time of event: June 17, 2000 @ 11:57 UT
Magnitude of target star: 8.6
Magnitude drop [mag]: 3.4
Estimated maximum duration [s]: 7.5
Path description: See above.
Goffin's original chart reference: A00_0612

The Occultation Path:

Approximate width [km]: 115
Uncertainty [path widths]: 0.9
Uncertainty in time [s]: 10
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.

Data for the target star:

Name: HIP 84192 = PPM 266554 = SAO 185147 = TYC 6820 144-1

Constellation: Ophiuchus

J2000 position [h,m,s; ^o,',"]: 17h 12m 36.458s; -27^o 01' 09.40"

Position source: Hipparcos

Estimated accuracy ["]: 0.01" (0.01", 0.01")

V mag [mag]: 8.57

B-V [mag]: +1.54

Remarks:

The target star is in southern Ophiuchus. It lies 3 degrees south-west of theta Ophiuchi (magnitude = 3.3) and 50' south-west of 36 Ophiuchi (magnitude = 4.3). The magnitude 6.8 star HIP 84144 = SAO 185137 lies only 6' to the west of the target star.
To see a detailed finder chart, click here.

Data for the minor planet:

Number, name: (164) Eva
Approx. diameter [km]: 110
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone)
Number of used observations: 47
Number of rejected observations: 5
Time covered by the observations: 1998 02 12 - 2000 06 09
RMS residuals ["] (RA,DE): 0.08", 0.08"
Estimated positional accuracy at epoch of event ["]: 0.09"

Data for the event:

UT date and time of least geocentric approach: 2000 June 17, 11:55.9 UT
Approx. V mag of minor planet at event [mag]: 11.9
Geocentric parallax of minor planet ["]: 6.150
Magnitude drop [mag]: 3.4
Estimated maximum duration [s]: 7.5
Apparent motion of minor planet ["/h]: 51.00
Angular distance to moon, phase of moon [deg,%]: 14, 100%
Update computed by: Jan Manek, Stefanik Observatory, Prague, Czech Republic.

Eva Update

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.

Use these links for further information:
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