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Updated: 2020 Oct 28, 20:47 UT
Event Rank : 94
(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 Dec 20 UT, the 63 km diameter asteroid (971) Alsatia will occult a 11.9 mag star in the constellation Gemini for observers along a path across Northern Territory, south-eastern Queensland and north-western New South Wales, passing over Coonabarrabran and Newcastle.
In the case of an occultation, the combined light of the asteroid and the star will drop by 1.19 mag to 12.65 mag (the magnitude of the asteroid) for at most 6.0 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Hugh Harris, astrometry for the asteroid kindly provided by Bill Owen, astrometry for the asteroid kindly provided by the IAU Minor Planet Center. This work has made use of data from the European Space Agency (ESA) mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia 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, in particular 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 589-032237 by 971 Alsatia on 2020 Dec 20
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
155 1 20 -36 0 0 16 59 27.3 16 323 -14 155 33 0 154 29 42 156 1 20 154 1 26 0.39
153 50 25 -35 0 0 16 59 31.7 17 323 -15 154 21 39 153 19 13 154 49 35 152 51 19 0.40
152 40 32 -34 0 0 16 59 36.5 18 324 -17 153 11 22 152 9 43 153 38 56 151 42 11 0.40
151 31 34 -33 0 0 16 59 41.6 20 325 -18 152 2 1 151 1 7 152 29 16 150 33 54 0.40
150 23 25 -32 0 0 16 59 47.0 21 325 -19 150 53 32 149 53 18 151 20 28 149 26 23 0.40
149 16 0 -31 0 0 16 59 52.8 22 326 -21 149 45 48 148 46 12 150 12 27 148 19 32 0.41
148 9 13 -30 0 0 16 59 58.9 24 327 -22 148 38 44 147 39 42 149 5 7 147 13 17 0.41
147 2 59 -29 0 0 17 0 5.4 25 327 -24 147 32 15 146 33 43 147 58 24 146 7 32 0.41
145 57 14 -28 0 0 17 0 12.2 26 328 -25 146 26 15 145 28 12 146 52 11 145 2 13 0.41
144 51 52 -27 0 0 17 0 19.3 28 329 -26 145 20 41 144 23 3 145 46 25 143 57 15 0.41
143 46 50 -26 0 0 17 0 26.8 29 329 -28 144 15 27 143 18 12 144 41 1 142 52 35 0.41
142 42 4 -25 0 0 17 0 34.6 30 330 -29 143 10 30 142 13 36 143 35 55 141 48 7 0.41
141 37 29 -24 0 0 17 0 42.7 32 331 -30 142 5 46 141 9 9 142 31 2 140 43 48 0.41
140 33 1 -23 0 0 17 0 51.2 33 331 -32 141 1 10 140 4 49 141 26 19 139 39 35 0.41
139 28 36 -22 0 0 17 0 59.9 34 332 -33 139 56 39 139 0 31 140 21 41 138 35 22 0.41
138 24 11 -21 0 0 17 1 9.1 36 333 -35 138 52 8 137 56 12 139 17 6 137 31 8 0.41
137 19 43 -20 0 0 17 1 18.5 37 333 -36 137 47 35 136 51 47 138 12 29 136 26 46 0.41
136 15 6 -19 0 0 17 1 28.3 38 334 -37 136 42 55 135 47 14 137 7 46 135 22 16 0.41
135 10 18 -18 0 0 17 1 38.4 40 335 -39 135 38 5 134 42 28 136 2 53 134 17 31 0.41
134 5 15 -17 0 0 17 1 48.8 41 335 -40 134 33 1 133 37 25 134 57 48 133 12 29 0.41
132 59 53 -16 0 0 17 1 59.6 42 336 -41 133 27 39 132 32 3 133 52 26 132 7 6 0.41
131 54 8 -15 0 0 17 2 10.7 44 337 -43 132 21 55 131 26 16 132 46 43 131 1 18 0.41
130 47 56 -14 0 0 17 2 22.1 45 338 -44 131 15 46 130 20 2 131 40 36 129 55 1 0.41
129 41 14 -13 0 0 17 2 33.8 46 338 -46 130 9 8 129 13 16 130 34 1 128 48 11 0.41
128 33 57 -12 0 0 17 2 45.9 48 339 -47 129 1 56 128 5 54 129 26 53 127 40 45 0.41
127 26 2 -11 0 0 17 2 58.3 49 340 -49 127 54 6 126 57 52 128 19 9 126 32 36 0.41
126 17 23 -10 0 0 17 3 11.1 50 341 -50 126 45 35 125 49 5 127 10 43 125 23 42 0.41
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