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Updated: 2020 Jul 01, 05:25 UT
Event Rank : 51
(The event Rank is a measure of the likelihood of observing an event, and is equal to the probability of at least one successful observation by a team of two observers spaced 1/8 path width just inside opposite sides of the predicted path. An event rank of 100 indicates that the prediction is expected to be very accurate).
THE UPDATED PATH
Note: The duration given in the line below is the interval during which the occultation shadow sweeps across the Earth - please see the minute markers on the map to determine the approximate time for your location.
On 2020 Aug 29 UT, the 72 km diameter asteroid (1868) Thersites will occult a 12.5 mag star in the constellation Pisces for observers along a somewhat uncertain path across south-eastern New South Wales, eastern Victoria and Tasmania.
In the case of an occultation, the combined light of the asteroid and the star will drop by 3.75 mag to 16.20 mag (the magnitude of the asteroid) for at most 5.3 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindlyprovided by Hugh Harris, astrometry for the asteroid kindly provided by BillOwen, astrometry for the asteroid kindly provided by the IAU Minor PlanetCenter.This work has made use of data from the European Space Agency (ESA)mission Gaia (http://www.cosmos.esa.int/gaia), processed by theGaia Data Processing and Analysis Consortium(DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, inparticular the institutions participating in the Gaia Multilateral Agreement.
Additional details of this and other events are available at Steve Preston's website at http://www.asteroidoccultation.com/
EVENT DETAILS SUMMARY :Important Note regarding Accuracy:
The uncertainty interval in path widths given above (and shown as a 1-sigma uncertainty ellipse on the plot) refers to RMS deviation and is applied as a +/- range. In other words, a path uncertainty of 1.0 path widths means that the actual center of the asteroid's shadow path should fall within plus or minus 1 path width of the plotted path center. However path errors larger than 1 sigma have been observed so observers should be alert for primary occultations within plus or minus 3 sigma of the updated path.
Further, almost all asteroidal satellites discovered so far have been found within 10 diameters of the asteroid (since this distance is deep enough within the gravitational well to be stable over long timescales). Therefore, if monitoring for secondary events, observing out to about 10 path-widths either side of the predicted track remains worthwhile.
We therefore recommend that you monitor for events if your observing location is up to +/- 10 path-widths from the predicted track. If not monitoring for occultations by secondary bodies you should observe from locations within 3 sigma of the nominal path.
In terms of time, the predictions are now usually accurate to about +/- 0.3 minute so you should be most attentive during the predicted minute of the event. However if intending to catch a potential satellite occultation you should start observing at least 10 times the predicted central duration before the predicted closest approach time for your location, and continue for a similar period afterwards.
Occultation of UCAC4-488-145331 by 1868 Thersites on 2020 Aug 29
Centre Star Star Sun Path Limits Error Limits Alt
E. Longitude Latitude U.T. Alt Az Alt Limit 1 Limit 2 Limit 3 Limit 4 Crn
o ' " o ' " h m s o o o o ' " o ' " o ' " o ' "
Longitude Longitude Longitude Longitude
139 50 38 -45 0 0 18 25 17.5 27 317 -30 138 36 3 141 7 5 135 36 30 144 28 3 1.90
140 59 12 -44 0 0 18 25 7.2 28 315 -30 139 44 14 142 16 7 136 44 4 145 38 51 1.90
142 10 43 -43 0 0 18 24 56.7 28 314 -29 140 55 12 143 28 20 137 54 1 146 53 26 1.90
143 25 26 -42 0 0 18 24 45.8 28 312 -29 142 9 8 144 43 58 139 6 30 148 12 11 1.90
144 43 38 -41 0 0 18 24 34.6 28 311 -28 143 26 19 146 3 20 140 21 44 149 35 30 1.90
146 5 37 -40 0 0 18 24 23.1 28 309 -27 144 47 1 147 26 49 141 39 56 151 3 58 1.90
147 31 49 -39 0 0 18 24 11.3 27 307 -26 146 11 37 148 54 53 143 1 24 152 38 17 1.91
149 2 45 -38 0 0 18 23 59.1 27 306 -25 147 40 33 150 28 9 144 26 26 154 19 24 1.91
150 39 4 -37 0 0 18 23 46.6 27 304 -24 149 14 24 152 7 22 145 55 29 156 8 35 1.91
152 21 37 -36 0 0 18 23 33.6 26 302 -23 150 53 52 153 53 33 147 29 0 158 7 40 1.91
154 11 31 -35 0 0 18 23 20.3 25 301 -22 152 39 53 155 48 6 149 7 39 160 19 17 1.92
156 10 18 -34 0 0 18 23 6.5 24 299 -20 154 33 41 157 52 58 150 52 11 162 47 44 1.92
158 20 10 -33 0 0 18 22 52.2 23 297 -18 156 37 0 160 11 3 152 43 41 165 40 42 1.93
Uncertainty in time = +/- 11 secs
Prediction of 2020 Jul 1.0
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