ASTROMETRIC UPDATE:
OCCULTATION BY (331) ETHERIDGEA - 2001 JANUARY 27
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[Prediction using OCCULT software including finder charts]
The path predicted by OCCULT runs tangentially to the surface of the Earth to the south of the Australian land mass.
UPDATE: 19 January 2001
This prediction update has been computed by Stephen Kerr based on astrometry from Ron Stone of the US Naval Observatory - Flagstaff Station. The ACT position of the target star has been used.
Summary:
This event was found by David Herald using the OCCULT software (Windows version 1.4) with the 'Goffin' catalogue of star positions. The predicted event runs tangential to the surface of the Earth to the south of the Australian land mass over the period 14:05 UT to 14:10 UT. Due to the high northern declination of the target star, most of the southern parts of Australia and New Zealand lie within 0.5" of the predicted path.
Astrometry intended for another event involving (331) Etheridgea crossing North America earlier on the same night has been used to update this event. The path change is very slight - around 0.5 of a path width to the north and around 10 seconds later. As such the path is still tangential to the Earth's surface and the probability of any event involving the main body of the asteroid being seen from the Australian or New Zealand land masses is low.
THE EVENT AT ONE GLIMPSE:
- Date and approx. UT time of event: January 27, 2001 @ 14:08 UT
- Magnitude of target star: 9.7
- Magnitude drop [mag]: 4.6
- Estimated maximum duration [s]: 6.3
- Path description: See above.
The Occultation Path:
- Approximate width [km]: --
- Map: See below
Data for the target star:
- Name: TYC 2451-01828-1
- Constellation: Gemini
- J2000 position [h,m,s; o,',"]: 7h 15m 09.044s; +31o 01' 16.49"
- Position source: ACT
- Estimated accuracy ["]: 0.08" (0.03", 0.08")
- V mag [mag]: 9.7
- B-V [mag]: +0.57
- Remarks:
- The target star is in central northern Gemini. It is around 1.2 degrees north-east of tau Geminorum (mag=4.4) and 37' west of the magnitude 6.2 star SAO 59964. A detailed finder chart is attached to the OCCULT prediction and can be reached by clicking here.
Data for the minor planet:
- Number, name: (331) Etheridgea
- Approx. diameter [km]: 74
- Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone)
- Number of used observations: 18
- Number of rejected observations: 0
- Time covered by the observations: 2000 11 10 - 2001 01 07
Data for the event:
- UT date and time of least geocentric approach: 2001 January 27, 14:08.4 UT
- Approx. V mag of minor planet at event [mag]: 14.3
- Geocentric parallax of minor planet ["]: 4.006
- Magnitude drop [mag]: 4.6
- Estimated maximum duration [s]: 6.3
- Apparent motion of minor planet ["/h]: 26.6
- Angular distance to moon, phase of moon [deg,%]: 126, 8%
- Update computed by: Stephen Kerr (Win OCCULT 1.4).
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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