RASNZ Occultation Section - Marianna Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (602) MARIANNA - 2001 AUGUST 27

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[Prediction using OCCULT software + finder charts]

The path given by Occult crosses northern New South Wales at low altitude before running through South Australia to the Eyre Peninsula area. The path then runs out into the Great Australian Bight missing southern Western Australia.

UPDATE: 24 August 2001

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.

Summary:

This updated path lies around two path widths to the north of that given by Occult and around 10 seconds later. The path now crosses southern Queensland on the northern outskirts Brisbane at very low altitude (around 5 degrees - 19:22 UT). Running southwest, the path crosses far northwestern New South Wales and central South Australia to the head of the Great Australian Bight (19:23 UT). It then runs across southern Western Australia with Esperence near the southern edge and Bunbury near the northern edge (19:24 UT).

The error tolerance on this calculation is quite small with Perth near the northern edge at 19:24 UT.

The magnitude drop for this event is quite small (only 1.2) and any observer who can comfortably see the target star will most probably be able to see the asteroid in the event of an occultation.

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 27, 2001 @ 19:23 UT
Magnitude of target star: 10.3
Magnitude drop [mag]: 1.2
Estimated maximum duration [s]: 11.2
Path description: See above.

The Occultation Path:

Approximate width [km]: 130
Uncertainty [path widths]: 0.5 (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 6363-00573-1 = PPM 239309
Constellation: Capricornus
J2000 position [h,m,s; ^o,',"]: 21h 45m 44.5930s; -15^o 23' 20.036"
Position source: UCAC
Estimated accuracy ["]: 0.042" (0.030", 0.030")
V mag [mag]: 10.3
B-V [mag]: +0.86
Remarks:
The target star is in eastern Capricornus. It lies only 48' northwest of delta Capricorni (magnitude 2.8).
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: (602) Marianna
Approx. diameter [km]: 124
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), AstDys
Number of used observations: 242
Number of rejected observations: 44
Time covered by the observations: 1906 02 23 - 2001 08 19
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.049", 0.046", 65°.

Data for the event:

UT date and time of least geocentric approach: 2001 August 27, 19:31.1 UT
Approx. V mag of minor planet at event [mag]: 11.6
Geocentric parallax of minor planet ["]: 5.778
Magnitude drop [mag]: 1.6
Estimated maximum duration [s]: 11.2
Apparent motion of minor planet ["/h]: 36.05
Angular distance to moon, phase of moon [deg,%]: 56, 70%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Marianna 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:
[Planetary Occultations] [Using the Predictions]
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[Asteroid Occultation Results]

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