RASNZ Occultation Section - Mathilde Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (253) MATHILDE - 2001 SEPTEMBER 24

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[Prediction using OCCULT software + finder charts]

The path given by Occult runs across the southern parts of the North Island of New Zealand as well as the northern part of the South Island.

UPDATE: 20 September 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 and Bill Owen of the Table Mountain Observatory supplemented with data from the AstDys database. The UCAC position of the target star has been used.

Summary:

This updated path lies around 2 path widths to the southeast of that given by OCCULT and around 1 minute later. The path runs from the Christchurch area at 8:07 UT to the southwest across the South Island of New Zealand. Wellington lies within the error band of this calculation at 8:06:30 UT.

(253) Mathilde is one of few asteroids that has been visited by spacecraft and is known to have a small satellite. It is not possible to predict the path of an occultation involving the satellite. Observers over all of New Zealand are urged to monitor this event.

Observers should note that the target star is quite faint (magnitude = 12) and that the asteroid is of virtually the same magnitude. In the event of an occultation, the magnitude fall will be very small (0.8) and difficult to perceive. The event may not be monitorable for observers with smaller telescopes.

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: September 24, 2001 @ 8:07 UT
Magnitude of target star: 12.0
Magnitude drop [mag]: 0.8
Estimated maximum duration [s]: 9.9
Path description: See above.

The Occultation Path:

Approximate width [km]: 58
Uncertainty [path widths]: 0.65 (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: GSC 5246 358 = TAC -03°17274
Constellation: Aquarius
J2000 position [h,m,s; ^o,',"]: 23h 11m 24.6535s; -3^o 49' 16.287"
Position source: UCAC
Estimated accuracy ["]: 0.041" (0.031", 0.031")
V mag [mag]: 12.0
Remarks:
The target star is in northern Aquarius near the border with Pisces. It lies 2.3 degrees northwest of phi Aquarii (magnitude = 4.2).
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: (253) Mathilde
Approx. diameter [km]: 58
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), TMO - Bill Owen, AstDys
Number of used observations: 659
Number of rejected observations: 35
Time covered by the observations: 1901 04 23 - 2001 09 16
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.043", 0.028", 74°.

Data for the event:

UT date and time of least geocentric approach: 2001 September 24, 7:51.5 UT
Approx. V mag of minor planet at event [mag]: 12.1
Geocentric parallax of minor planet ["]: 9.001
Magnitude drop [mag]: 0.8
Estimated maximum duration [s]: 9.9
Apparent motion of minor planet ["/h]: 29.61
Angular distance to moon, phase of moon [deg,%]: 77, 49%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Mathilde 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]
[Observing Details] [Timing Details] [Reporting Details] [Report Form]
[Asteroid Occultation Results]

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