RASNZ Occultation Section - Patientia Occultation (July 6) Update

ASTROMETRIC UPDATE:
OCCULTATION BY (451) PATIENTIA - 1999 JULY 6

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

Both the Goffin and OCCULT predictions suggest a very favourable path across southern New Zealand.

UPDATE: 2 July 1999

This prediction update is supplied by Jan Manek of the Stefanik Observatory, Prague, and is based on USNO/Flagstaff and Table Mountain astrometry for the minor planet and the GSC 1.2 star position.

Note that the accuracy of the star position in the GSC 1.2 catalog is 0.3". The photographic magnitude of 12.05 given in Goffin's prediction is in fact a visual magnitude. Therefore the brightness drop at occultation will be only about 0.5 magnitudes, which is right on the limit of reliable visual detection. Notwithstanding this, the path is exceptionally well-placed for many of the photometric observatories within New Zealand

Summary:

The update astrometry gives a path very much in accord with both the Goffin and OCCULT predictions, with a time approximately 30 seconds later than Goffin's.

Although this will be a difficult event for visual observers, it is quite within the reach of photometric instruments. At present, the update path directly crosses photometric sites at Mt John, Christchurch, Blenheim and Wellington, New Zealand, with the Auckland Observatory less than one track width away. (Track uncertainty is ~3 track widths). All photometric observatories are encouraged to monitor this event.

Approx time for Auckland: 14h 59m UT

Approx time for Wellington/Blenhem: 14h 59.5m UT

Approx time for Christchurch/Mt John: 15h 00m UT

THE EVENT AT ONE GLIMPSE:

Date and approx. UT time of event: July 6, 1999 @ 15:00 UT
Magnitude of target star: 12.05
Magnitude drop [mag]: ~0.5
Estimated maximum duration [s]: 16.7
Path description: The path runs across substantial parts of New Zealand.

The Occultation Path:

Approximate width [km]: 240
Uncertainty [path widths]: 3
Uncertainty in time [s]: 45
Map: See below
Remarks: Uncertainities are given on the basis of the nominal errors in the observations.
Circles along the path are OCCULT calculated exact centerline points.

Data for the target star:

Name: GSC 6846 01083
Constellation: Sagittarius
J2000 position [h,m,s; o,',"]: 18h 00m 53.610s; -25o 24' 20.30"
Position source: GSC 1.2
Estimated accuracy ["]: 0.3"
V mag [mag]: 11.37
B-V [mag]: ???
Remarks:

Data for the minor planet:

Number, name: (451) Patientia
Approx. diameter [km]: 230
Orbit source: calculation Manek
Source of used astrometry: USNO/Flagstaff (Ron Stone) and Table Mountain Observatory (Bill Owen)
Number of used observations: 33 USNO + 14 TMO
Number of rejected observations: 0
Time covered by the observations: 1998 03 04 - 1999 06 26
Rms residuals ["] (RA,DE): 0.06", 0.07"
Estimated positional accuracy at epoch of event ["]: 0.07"

Data for the event:

UT date and time of least geocentric approach: 15:03:42 UT
Approx. V mag of minor planet at event [mag]: 12.05
Geocentric parallax of minor planet ["]: 3.87
Magnitude drop [mag]: ~0.5
Estimated maximum duration [s]: 16.7
Apparent motion of minor planet ["/h]: 30.04
Angular distance to moon, phase of moon [deg,%]: 105, 49%

Patientia Update (July 6)

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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