RASNZ Occultation Section - Devosa Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (337) DEVOSA - 2001 MAY 30

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

The path given by Edwin Goffin crosses the North Island of New Zealand just to the south of Auckland. Running west, the path crosses the New South Wales coast around Wollongong, clips the head of the Great Australian Bight before leaving the Western Australian coastline around Carnarvon. The path given by Occult lies around 1.5 path widths to the north crossing the North Island of New Zealand around Whangarei, metropolitan Sydney in New South Wales and just to the south of Exmouth in Western Australia.

UPDATE: 27 May 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 and Gordon Garradd of Loomberah, New South Wales. The UCAC1 position of the target star has been used.

Summary:

This updated path lies around one path width to the north of that given by Goffin and around 30 seconds later. The new path crosses the North Island of New Zealand including Whangarei at 13:27 UT. Auckland lies well within the error calculation for the event at essentially the same time as Whangarei. In New South Wales, the path covers the southern parts of metropolitan Sydney with the whole of the Wollongong to Lake Macquarie area within the error margin at 13:30:20 UT. Canberra also lies near the southern edge of the error margin some 10 seconds later. The path passes very close to Broken Hill at 13:32 UT before running further west. On the Western Australian coastline, the path passes between Exmouth and Carnarvon at 13:38 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: May 30, 2001 @ 13:35 UT
Magnitude of target star: 11.12
Magnitude drop [mag]: 1.7
Estimated maximum duration [s]: 7.6
Path description: See above.
Goffin's original chart reference: A01_0518

The Occultation Path:

Approximate width [km]: 59
Uncertainty [path widths]: 1.3 (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 6731-00975-1
Constellation: Hydra
J2000 position [h,m,s; ^o,',"]: 14h 16m 40.840s; -24^o 22' 00.10"
Position source: UCAC1
Estimated accuracy ["]: 0.054" (0.039", 0.038")
V mag [mag]: 11.12
Remarks:
The target star is in eastern Hydra near the border with Libra. It lies around 3.3 degrees northeast of pi Hydrae (magnitude = 3.3)

Data for the minor planet:

Number, name: (337) Devosa
Approx. diameter [km]: 63.2
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), Gordon Garradd
Number of used observations: 65
Number of rejected observations: 11
Time covered by the observations: 1998 06 19 - 2001 05 23
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.022", 0.018", 118°.

Data for the event:

UT date and time of least geocentric approach: 2001 May 30, 13:35.9 UT
Approx. V mag of minor planet at event [mag]: 12.61
Geocentric parallax of minor planet ["]: 5.24
Magnitude drop [mag]: 1.7
Estimated maximum duration [s]: 7.6
Apparent motion of minor planet ["/h]: 24.73
Angular distance to moon, phase of moon [deg,%]: 54, 57%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Devosa 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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