RASNZ Occultation Section - Nemausa Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (51) NEMAUSA - 2001 SEPTEMBER 17

CHECK THIS PAGE REGULARLY FOR FURTHER UPDATES AND CHANGES TO THE TRACK.

YOU MUST RELOAD THIS PAGE USING YOUR BROWSER'S
RELOAD/REFRESH BUTTON TO OBTAIN UPDATES!

[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

After crossing the Tasman Sea, Goffin's path passes diagonally through Bass Strait clipping Cape Howe and the northwest corner of Tasmania. The path given by OCCULT is virtually identical.

UPDATE: 15 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 combined with Tycho 2 proper motion data.

Summary:

This updated path lies slightly less than a path width to the southeast of that given by Goffin with little difference in expected times. The path clears the Cape Howe area in far eastern Victoria and crosses the northwestern half of Tasmania including Launceston and Burnie (10:07 UT). Hobart lies near the edge of the error band of this calculation.

Observers should note that the magnitude fall for this event is expected to be ONLY 0.5. This will be virtually impossible to observe visually but careful operators of video equipment should be able to detect this event. If the asteroid magnitude estimate is in error - quite possible - the magnitude fall may be significantly larger or smaller.

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 17 : 10:06 UT
Magnitude of target star: 11.67
Magnitude drop [mag]: 0.5 !!!
Estimated maximum duration [s]: 17.5
Path description: See above.
Goffin's original chart reference: A01_0910

The Occultation Path:

Approximate width [km]: 148
Uncertainty [path widths]: 0.27 (1 sigma)
Map: See below

Data for the target star:

Name: TYC 5787-00951-1
Constellation: Aquarius
J2000 position [h,m,s; ^o,',"]: 21h 40m 26.6501s; -8^o 10' 33.871"
Position source: UCAC + TYC 2 Proper Motion
Estimated accuracy ["]: 0.043" (0.030", 0.031")
V mag [mag]: 11.67
Remarks:
The target star is southern Aquarius very close to the border with Capricornus. It lies 44' southeast of xi Aquari (magnitude = 4.7).

Data for the minor planet:

Number, name: (51) Nemausa
Approx. diameter [km]: 152
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), TMO - Bill Owen, AstDys
Number of used observations: 3447
Number of rejected observations: 276
Time covered by the observations: 1906 06 27 - 2001 09 12

Data for the event:

UT date and time of least geocentric approach: 2001 September 17, 9:58.6 UT
Approx. V mag of minor planet at event [mag]: 11.13
Geocentric parallax of minor planet ["]: 5.53
Magnitude drop [mag]: 0.5
Estimated maximum duration [s]: 17.5
Apparent motion of minor planet ["/h]: 27.23
Angular distance to moon, phase of moon [deg,%]: 149, 0%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit).

Nemausa 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]

This page may have been updated since 15 September 2001.
Hit your browser's RELOAD button to get the latest version.
[Site Map] [What's an Occultation?]
[Total Occultations] [Grazing Occultations] [Planetary Occultations] [Jovian Satellite Eclipses]
[Timing Occultations] [Reporting Observations] [Coming Events] [Software]
[About Us] [Publications] [Membership] [Links]

[Top of Page][Return to Home Page]