RASNZ Occultation Section - Dembowska Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (349) DEMBOWSKA - 2000 MAY 17

THIS UPDATE REPLACES THE PREVIOUS UPDATE OF 11 MAY.

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

[Detailed finder chart by Jan Manek]

Goffin's path crosses the North Island of New Zealand including Auckland before crossing the Tasman Sea to cross southern Victoria. The path includes Melbourne near it southern edge before passing just to the south of Kangaroo Island. The path then clips the southern most parts of Western Australia including Albany. The OCCULT path lies around 0.5 of a path width to the south with virtually no shift in time.

UPDATE: 12 May 2000

This prediction update has been computed by Jan Manek based on astrometry from Ron Stone of the US Navel Observatory - Flagstaff Station, Bill Owen of TMO and the Hipparcos astrometric satellite mission. The Tycho 2 position of the target star has been used.

Summary:

The update path lies around 1 path width to the south of that given by Goffin with little change of time. The path crosses the central part of the North Island of New Zealand at 14:29 UT. The path includes Tauranga and Hamilton with Auckland just to the north. The path then crosses the southern tips of Victoria at Wilson's Promontory (17:32 UT) and at Cape Otway. The path runs very close to the Western Australian coastline at and to the west of Albany at 14:35 UT.

Auckland and Melbourne observers are urged to monitor from sites at and to the south of their respective cities to improve the likelihood of detecting a positive event and the possibility of providing multiple chords to allow an accurate diameter/profile to be determined for 349 Debowska !!

Note that with an expected magnitude of 10.2, observers can expect to be able to see the asteroid. In this case, an occultation will appear as a dimming rather than a disapperence of the star. Careful attention is therefore required to monitor this event. Observations made by non-visual techniques (eg. video) are most welcome.

The proximity of the full moon (only 9 degrees away) will also complicate the observation and may make field identification difficult.

THE EVENT AT ONE GLIMPSE:

Date and approx. UT time of event: May 17, 2000 @ 14:30 UT
Magnitude of target star: 9.2
Magnitude drop [mag]: 1.4
Estimated maximum duration [s]: 10.7
Path description: See above.
Goffin's original chart reference: A00_0515

The Occultation Path:

Approximate width [km]: 150
Uncertainty [path widths]: 1.1
Uncertainty in time [s]: 15
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 6182 371-1 = PPM 263933 = SAO 183258

Constellation: Libra

J2000 position [h,m,s; ^o,',"]: 15h 12m 06.006s; -22^o 21' 51.10"

Position source: TYC-2

Estimated accuracy ["]: 0.04" (0.03", 0.03")

V mag [mag]: 9.23

B-V [mag]: +1.61 -->

Remarks:

The target star is 3.5 degrees north-east of sigma Librae (mag = 3.3). The mag 5.5 star SAO 183328 lies 1 degree to the east of the target star. Beware of the 12th mag star GSC 6181 738 only 1.8' to the south-west of the target star.
To see a detailed finder chart, click here.

Data for the minor planet:

Number, name: (349) Dembowska
Approx. diameter [km]: 143
Source of used astrometry: US Navel Observatory - Flagstaff Station (Ron Stone), TMO (Bill Owen), Hipparcos
Number of used observations: 64 USNO, 25 TMO, 111 HIP
Number of rejected observations: 1 USNO, 2 TMO, 1 HIP
Time covered by the observations: 1990 01 19 - 2000 05 06
RMS residuals ["] (RA,DE): 0.08", 0.08"
Estimated positional accuracy at epoch of event ["]: 0.07"

Data for the event:

UT date and time of least geocentric approach: 2000 May 17 14:33.5 UT
Approx. V mag of minor planet at event [mag]: 10.2
Geocentric parallax of minor planet ["]: 4.156
Magnitude drop [mag]: 1.4
Estimated maximum duration [s]: 10.7
Apparent motion of minor planet ["/h]: 31.49
Angular distance to moon, phase of moon [deg,%]: 9, 99%
Update computed by: Jan Manek

Dembowska 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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