RASNZ Occultation Section - Freia Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (76) FREIA - 2002 JANUARY 14

The prediction given by Goffin shows a path just missing the far northern tip of New Zealand at low altitude before running from southeastern Queensland to the Kimberley area of Western Australia. The path given by Occult using the TAC star position lies only a fraction of a path width to the south.

UPDATE: 8 JANUARY 2002

THE UPDATED PATH

Freia Update

This updated path lies around 0.4 of a path width to the south of that given by Goffin and around 40 seconds later. Due to twilight and low altitude (sun = 7 degrees below horizon and star altitude = 18 degrees), observation from the far northern tip of the North Island may not be practical. Across the Tasman Sea, the path covers the Queensland coastline between central Brisbane and Hervey Bay at 17:04 UT. Further west, the path crosses Tennant Creek in the Northern Territory around 17:07 UT before leaving the Australian mainland around the King Sound area at 17:08 UT.

The error margin on this calculation is such that all of Brisbane stands a good chance of seeing an occultation and observations will be worthwhile between Coff's Harbour in New South Wales and Mackay in central Queensland.

Calculation Source

This prediction update has been computed by Steve Preston of Medina, Washington (state) in the United States based on astrometry from Ron Stone of the US Naval Observatory - Flagstaff Station supplemented with data from the AstDys database. The UCAC position of the target star has been used combined with proper motion data from Tycho 2.

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

EVENT DETAILS SUMMARY:

Date and approx. UT time of event: 2002 January 14 - 17:04 UT
Magnitude of target star: 11.22
Magnitude drop [mag]: 1.2
Estimated maximum duration [s]: 17.3
Angular distance to moon, phase of moon [deg,%]: 173, 1%
Goffin's original chart reference: A02_0111

The Occultation Path:

Approximate width [km]: 209
Uncertainty [path widths]: +/- 0.45 (1 sigma)
Remarks: Uncertainities are given on the basis of the nominal star position errors and the expected asteroid positional accuracy.

Data for the target star:

Name: TYC 1379-00596-1
Constellation: Cancer
J2000 position [h,m,s; ^o,',"]: 8h 26m 45.4614s; +15^o 54' 40.566"
Position source: UCAC + Tycho 2 PM
Estimated accuracy ["]: 0.041" (0.030", 0.030")
V mag [mag]: 11.2
Remarks:
The target star is central Cancer. It lies 2.4 degrees south west of theta Cancri (magnitude = 5.4).

Data for the minor planet:

Number, name: (76) Freia
Approx. diameter [km]: 190
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), AstDys
Number of used observations: 764
Number of rejected observations: 92
Time covered by the observations: 1906 10 18 - 2002 01 03
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit).

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:
[Planetary Occultations] [Using the Predictions]
[Observing Details] [Timing Details] [Reporting Details] [Report Form]
[Asteroid Occultation Results]

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