RASNZ Occultation Section - Amata Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (1035) AMATA - 2001 JUNE 24

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

The path given by Edwin Goffin clips the northern tip of the North Island of New Zealand, crosses southern Victoria including Melbourne as well as the south western cornor of Western Australia. The path given by Occult lies around 0.3" to the south and 4 minutes earlier.

UPDATE: 20 June 2001

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 historical data from the AstDys database. The UCAC 1 position of the target star has been used.

Summary:

This update indicates a shift of around 0.3" to the south and around 15 seconds later than that given by Goffin. The path crosses the central parts of the North Island of New Zealand around 14:03 UT. The path includes much of East Cape, Whakatane and Rotorua with Tauranga near the north edge. The path uncertainty is quite large and in fact most of the North Island stands a good chance of observing an occultation.

Across the Tasman Sea, the path crosses central Tasmania at 14:07 UT. All of Tasmania lies within a reasonable error band for this calculation with Melbourne only slightly beyond the northern edge (14:07:15 UT). The nominal path does not make landfall in Western Australia but runs closely parallel between Albany and Cape Leeuwin (14:12 UT). Perth lies just to the north of the northern error band limit.

Additional details of this and other events are available at Steve Preston's website at http://www.oz.net/~stevepr/Asteroids/asteroid.htm

THE EVENT AT ONE GLIMPSE:

Date and approx. UT time of event: 24 June 2001 @ 14:07 UT
Magnitude of target star: 11.57
Magnitude drop [mag]: 3.1
Estimated maximum duration [s]: 6.1
Path description: See above.
Goffin's original chart reference: A01_0640

The Occultation Path:

Approximate width [km]: 58
Uncertainty [path widths]: 2.6 (1 sigma error band)
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: TYC 8315-00802-1
Constellation: Norma
J2000 position [h,m,s; ^o,',"]: 16h 07m 40.716s; -47^o 50' 28.49"
Position source: UCAC 1
Estimated accuracy ["]: 0.042" (0.030", 0.031")
V mag [mag]: 11.57
B-V [mag]: +1.36
Remarks:
The target star is in central Norma. The star lies 1.3 degrees southwest of theta Normae (magnitude = 5.1).

Data for the minor planet:

Number, name: (1035) Amata
Approx. diameter [km]: 56.8
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), AstDys
Number of used observations: 279
Number of rejected observations: 17
Time covered by the observations: 1913 10 31 - 2001 04 17
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.142", 0.079", 91°.

Data for the event:

UT date and time of least geocentric approach: 2001 June 24, 14:10.5 UT
Approx. V mag of minor planet at event [mag]: 14.64
Geocentric parallax of minor planet ["]: 4.64
Magnitude drop [mag]: 3.1
Estimated maximum duration [s]: 6.1
Apparent motion of minor planet ["/h]: 24.53
Angular distance to moon, phase of moon [deg,%]: 113, 13%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Amata 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.

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