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Updated: 2013 Jan 24, 04:27 UT
Event Rank : 87
(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 2013 Jan 31 UT, the 80 km diameter asteroid (925) Alphonsina will occult a 12.4 mag star in the constellation Auriga for observers along a path beginning near Bundaberg, running across south-east Queensland, New South Wales, passing over Coonabarrabran and Albury and eastern Victoria, finishing over Wilsons Promontory during late evening twilight.
In the case of an occultation, the combined light of the asteroid and the star will drop by 0.8 mag to 12.4 mag (the magnitude of the asteroid) for at most 7.8 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Hugh Harris, TMO astrometry for the asteroid kindly provided by Bill Owen, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: .
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 2UCAC 42902792 by 925 Alphonsina on 2013 Jan 31
Centre Star Star Sun Path Limits Error Limits
E. Longitude Latitude U.T. Alt Az Alt Limit 1 Limit 2 Limit 3 Limit 4
o ' " o ' " h m s o o o o ' " o ' " o ' " o ' "
Longitude Longitude Longitude Longitude
143 8 11 -45 0 0 10 26 16 11 16 -5 142 34 17 143 42 4 141 55 38 144 20 41
143 38 25 -44 0 0 10 26 14 12 16 -6 143 5 6 144 11 43 142 27 6 144 49 42
144 8 8 -43 0 0 10 26 11 14 16 -7 143 35 21 144 40 54 142 57 59 145 18 16
144 37 23 -42 0 0 10 26 8 15 15 -8 144 5 7 145 9 39 143 28 20 145 46 26
145 6 12 -41 0 0 10 26 5 16 15 -9 144 34 26 145 37 59 143 58 13 146 14 13
145 34 39 -40 0 0 10 26 2 17 15 -9 145 3 20 146 5 58 144 27 38 146 41 41
146 2 45 -39 0 0 10 25 59 18 14 -10 145 31 52 146 33 38 144 56 40 147 8 52
146 30 32 -38 0 0 10 25 55 19 14 -11 146 0 3 147 1 0 145 25 20 147 35 46
146 58 2 -37 0 0 10 25 51 20 14 -12 146 27 57 147 28 7 145 53 40 148 2 27
147 25 17 -36 0 0 10 25 47 21 13 -13 146 55 34 147 55 0 146 21 43 148 28 55
147 52 19 -35 0 0 10 25 43 22 13 -13 147 22 57 148 21 41 146 49 29 148 55 12
148 19 9 -34 0 0 10 25 38 23 13 -14 147 50 7 148 48 12 147 17 2 149 21 20
148 45 48 -33 0 0 10 25 33 24 13 -15 148 17 5 149 14 33 147 44 22 149 47 20
149 12 19 -32 0 0 10 25 28 25 12 -16 148 43 54 149 40 46 148 11 31 150 13 13
149 38 43 -31 0 0 10 25 23 26 12 -17 149 10 34 150 6 53 148 38 30 150 39 1
150 5 0 -30 0 0 10 25 18 27 12 -18 149 37 7 150 32 55 149 5 22 151 4 45
150 31 13 -29 0 0 10 25 12 28 11 -19 150 3 35 150 58 52 149 32 6 151 30 26
150 57 22 -28 0 0 10 25 7 29 11 -19 150 29 58 151 24 47 149 58 45 151 56 5
151 23 28 -27 0 0 10 25 1 30 11 -20 150 56 17 151 50 40 150 25 20 152 21 43
151 49 33 -26 0 0 10 24 55 31 11 -21 151 22 35 152 16 33 150 51 51 152 47 22
152 15 37 -25 0 0 10 24 48 32 10 -22 151 48 51 152 42 26 151 18 21 153 13 1
152 41 42 -24 0 0 10 24 42 33 10 -23 152 15 7 153 8 20 151 44 49 153 38 43
153 7 49 -23 0 0 10 24 35 35 10 -24 152 41 23 153 34 17 152 11 18 154 4 28
153 33 58 -22 0 0 10 24 28 36 9 -24 153 7 42 154 0 16 152 37 48 154 30 18
154 0 11 -21 0 0 10 24 21 37 9 -25 153 34 4 154 26 21 153 4 20 154 56 12
154 26 29 -20 0 0 10 24 14 38 9 -26 154 0 30 154 52 30 153 30 54 155 22 13
154 52 52 -19 0 0 10 24 7 39 8 -27 154 27 0 155 18 46 153 57 34 155 48 20
155 19 21 -18 0 0 10 23 59 40 8 -28 154 53 36 155 45 8 154 24 18 156 14 35
Uncertainty in time = +/- 4 secs
Prediction of 2013 Jan 24.0
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