RASNZ Occultation Section - Ekard Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (694) EKARD - 2000 MAY 12

THIS UPDATE REPLACES THE PREVIOUS UPDATE OF 6 MAY.

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

[Detailed finder chart by Jan Manek]

Goffin's predicted path crosses the southern Western Australian coast just west of Esperence passing to the northwest leaving the coastline in the Geraldton/Kalbarri area. The path predicted by OCCULT lies around three path widths or 0.4" to the east entering Western Australia east of Esperence and running to the northwest covering the Exmouth/North West Cape area. The OCCULT path is around 20 seconds earlier than that given by Goffin.

UPDATE: 9 May 2000

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

Summary:

This update places the path 1.5 path widths to the north-east of Goffin's prediction and 0.2 of a minute later. The path crosses the southern Western Australian coastline just east of Esperence (17:40:20 UT) running to the north-west. The path crosses the coast again at Carnarvon (17:42:30 UT).

The path also crosses northern Sri Lanka (17:50 UT) and southern India (17:51 UT) and southern Iran at low altitude (17:53 UT).

THE EVENT AT ONE GLIMPSE:

Date and approx. UT time of event: May 12, 2000 @ 17:41 UT
Magnitude of target star: 9.1
Magnitude drop [mag]: 3.6
Estimated maximum duration [s]: 9.3
Path description: See above.
Goffin's original chart reference: A00_0525

The Occultation Path:

Approximate width [km]: 95
Uncertainty [path widths]: 1.5
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.

Data for the target star:

Name: HIP 84058 = PPM 232717 = SAO 160342 = TYC 6232-00821-1

Constellation: Ophiuchus

J2000 position [h,m,s; ^o,',"]: 17h 11m 06.167s; -15^o 13' 04.91"

Position source: HIP

Estimated accuracy ["]: 0.02" (0.01", 0.01")

V mag [mag]: 9.14

B-V [mag]: +0.43

Remarks:

The target star is 32' NNE of eta Oph (Mag = 2.4).
To see a detailed finder chart, click here.

Data for the minor planet:

Number, name: (694) Ekard
Approx. diameter [km]: 91
Source of used astrometry: US Navel Observatory - Flagstaff Station (Ron Stone)
Number of used observations: 42
Number of rejected observations: 3
Time covered by the observations: 1998 02 12 - 2000 05 05
RMS residuals ["] (RA,DE): 0.11", 0.10"
Estimated positional accuracy at epoch of event ["]: 0.11"
Remarks: Goffin's chart gives a diameter of 92.7 km.

Data for the event:

UT date and time of least geocentric approach: 2000 May 12 17:42.9 UTC
Approx. V mag of minor planet at event [mag]: 12.7
Geocentric parallax of minor planet ["]: 5.898
Magnitude drop [mag]: 3.6
Estimated maximum duration [s]: 9.3
Apparent motion of minor planet ["/h]: 32.46
Angular distance to moon, phase of moon [deg,%]: 93, 69%
Update computed by: Jan Manek

Ekard Update

Ekard Update - Asia

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.

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