RASNZ Occultation Section - Westphalia Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (930) WESTPHALIA - 2001 AUGUST 26

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[Prediction using OCCULT software + finder charts]

The path given by Occult runs for the far southeastern corner of South Australia north along Cape York Peninsula in Queensland and then across Papua New Guinea.

UPDATE: 24 August 2001

This prediction update has been computed by Steve Preston of Medina, Washington (state) in the United States based on data from the AstDys database. The Tycho 2 position of the target star has been used.

Summary:

This updated path lies around 0.3" to the west of that given by Occult and just over a minute later. The path crosses the Eyre Peninsula in South Australia (19:10 UT) before running north across remote central Australia. It emerges into the Gulf of Carpentaria around the Queensland/Northern Territory border at 19:12 UT before crossing the eastern parts of Irian Jaya (19:14 UT).

The error tolerance on this calculation is quite large and Adelaide lies well within the error band at 19:10 UT.

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: August 26, 2001 @ 19:12 UT
Magnitude of target star: 10.0
Magnitude drop [mag]: 5.4
Estimated maximum duration [s]: 3.7
Path description: See above.

The Occultation Path:

Approximate width [km]: 37
Uncertainty [path widths]: 6.9 (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 1773-01179-1 = PPM 91484
Constellation: Aries
J2000 position [h,m,s; ^o,',"]: 02h 15m 22.7570s; +26^o 17' 56.636"
Position source: Tycho 2
Estimated accuracy ["]: 0.044" (0.031", 0.035")
V mag [mag]: 10.0
B-V [mag]: +1.15
Remarks:
The target star is in far northwestern Aries. It lies only 31' north of 20 Arietis (magnitude = 5.8) and 3.2 degrees northeast of Hamal (alpha Arietis - magnitude = 2.0)
A set of finder charts are available with the Occult prediction and can be viewed by clicking here.

Data for the minor planet:

Number, name: (930) Westphalia
Approx. diameter [km]: 36
Source of used astrometry: AstDys
Number of used observations: 132
Number of rejected observations: 18
Time covered by the observations: 1916 02 24 - 2001 07 28
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.206", 0.047", 65°.

Data for the event:

UT date and time of least geocentric approach: 2001 August 26, 19:19.0 UT
Approx. V mag of minor planet at event [mag]: 15.4
Geocentric parallax of minor planet ["]: 5.285
Magnitude drop [mag]: 5.4
Estimated maximum duration [s]: 3.7
Apparent motion of minor planet ["/h]: 29.23
Angular distance to moon, phase of moon [deg,%]: 143, 60%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Westphalia 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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