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Updated: 2009 JUL 29, 22:55 UT
Event Rank : 59
(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 2009 Aug 25 UT, the 172 km diameter asteroid (747) Winchester will occult a 13.1 mag star in the constellation Sagittarius for observers along a wide path across Australia from Queensland to South Australia. Beginning in Queensland between Cairns and Gladstone, passing through Australia and western parts of NSW and VIC, and ending between Ceduna and Warrnambool.
In the case of an occultation, the combined light of the asteroid and the star will drop by 0.4 mag to 12.2 mag (the magnitude of the asteroid) for at most 17.8 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Alice Monet, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: UCAC.
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.
Centre Star Star Sun Path Limit1 Path Limit2 Error Limit1 Error Limit2
E. Longitude Latitude U.T. Alt Az Alt
o ' " o ' " h m s o o o o ' " o ' " o ' " o ' " o ' " o ' " o ' " o ' "
Longitude Latitude Longitude Latitude Longitude Latitude Longitude Latitude
152 28 33 -17 8 23 16 17 49 17 254 -54 155 3 35 -16 50 17 150 12 6 -17 19 36 162 58 11 -15 18 47 146 1 53 -17 28 52
151 12 24 -18 13 42 16 17 59 18 255 -55 153 36 43 -17 59 46 149 3 2 -18 22 5 160 18 12 -16 55 11 145 2 1 -18 27 27
150 3 2 -19 16 38 16 18 8 20 256 -56 152 19 24 -19 5 52 147 59 10 -19 22 44 158 19 34 -18 16 50 144 5 37 -19 24 48
148 59 8 -20 17 38 16 18 18 21 256 -57 151 9 21 -20 9 24 146 59 39 -20 21 52 156 42 4 -19 30 56 143 12 14 -20 21 7
147 59 46 -21 17 5 16 18 28 22 257 -57 150 5 9 -21 10 54 146 3 51 -21 19 43 155 18 5 -20 40 16 142 21 31 -21 16 31
147 4 15 -22 15 13 16 18 38 23 257 -58 149 5 44 -22 10 45 145 11 16 -22 16 29 154 3 44 -21 46 13 141 33 10 -22 11 7
146 12 5 -23 12 14 16 18 48 24 258 -58 148 10 22 -23 9 15 144 21 30 -23 12 18 152 56 43 -22 49 37 140 46 57 -23 5 1
145 22 50 -24 8 17 16 18 58 25 259 -59 147 18 29 -24 6 35 143 34 16 -24 7 19 151 55 34 -23 51 2 140 2 40 -23 58 18
144 36 11 -25 3 32 16 19 7 26 259 -59 146 29 40 -25 2 57 142 49 17 -25 1 37 150 59 16 -24 50 50 139 20 9 -24 51 2
143 51 52 -25 58 3 16 19 17 26 260 -59 145 43 34 -25 58 28 142 6 21 -25 55 18 150 7 4 -25 49 19 138 39 16 -25 43 17
143 9 41 -26 51 56 16 19 27 27 261 -59 144 59 54 -26 53 14 141 25 18 -26 48 26 149 18 24 -26 46 40 137 59 53 -26 35 5
142 29 26 -27 45 16 16 19 37 28 261 -59 144 18 27 -27 47 22 140 45 59 -27 41 4 148 32 51 -27 43 5 137 21 53 -27 26 31
141 50 58 -28 38 7 16 19 47 28 262 -59 143 39 1 -28 40 57 140 8 16 -28 33 17 147 50 6 -28 38 41 136 45 12 -28 17 36
141 14 11 -29 30 32 16 19 56 29 263 -59 143 1 27 -29 34 2 139 32 2 -29 25 7 147 9 51 -29 33 34 136 9 44 -29 8 23
140 38 56 -30 22 34 16 20 6 30 264 -59 142 25 37 -30 26 41 138 57 13 -30 16 37 146 31 54 -30 27 51 135 35 26 -29 58 53
140 5 10 -31 14 17 16 20 16 30 264 -59 141 51 25 -31 18 57 138 23 44 -31 7 49 145 56 4 -31 21 36 135 2 14 -30 49 10
139 32 47 -32 5 41 16 20 26 31 265 -59 141 18 46 -32 10 53 137 51 30 -31 58 46 145 22 13 -32 14 52 134 30 4 -31 39 14
139 1 43 -32 56 51 16 20 36 31 266 -59 140 47 34 -33 2 31 137 20 28 -32 49 29 144 50 14 -33 7 45 133 58 54 -32 29 8
138 31 55 -33 47 48 16 20 45 32 267 -59 140 17 45 -33 53 55 136 50 36 -33 40 1 144 20 0 -34 0 16 133 28 42 -33 18 52
138 3 20 -34 38 33 16 20 55 32 267 -58 139 49 17 -34 45 5 136 21 50 -34 30 23 143 51 27 -34 52 28 132 59 25 -34 8 29
137 35 56 -35 29 8 16 21 5 32 268 -58 139 22 8 -35 36 4 135 54 9 -35 20 36 143 24 31 -35 44 25 132 31 2 -34 57 59
137 9 40 -36 19 36 16 21 15 33 269 -57 138 56 13 -36 26 54 135 27 30 -36 10 43 142 59 8 -36 36 7 132 3 30 -35 47 25
136 44 32 -37 9 57 16 21 25 33 270 -57 138 31 33 -37 17 36 135 1 53 -37 0 44 142 35 17 -37 27 38 131 36 50 -36 36 47
136 20 30 -38 0 13 16 21 34 33 270 -57 138 8 5 -38 8 11 134 37 16 -37 50 42 142 12 56 -38 18 59 131 10 59 -37 26 7
135 57 34 -38 50 26 16 21 44 33 271 -56 137 45 50 -38 58 42 134 13 39 -38 40 37 141 52 4 -39 10 11 130 45 57 -38 15 25
135 35 43 -39 40 36 16 21 54 34 272 -56 137 24 45 -39 49 10 133 51 1 -39 30 30 141 32 39 -40 1 17 130 21 44 -39 4 43
135 14 56 -40 30 45 16 22 4 34 273 -55 137 4 53 -40 39 35 133 29 22 -40 20 23 141 14 43 -40 52 18 129 58 19 -39 54 3
134 55 14 -41 20 55 16 22 14 34 273 -55 136 46 12 -41 30 0 133 8 42 -41 10 17 140 58 15 -41 43 15 129 35 41 -40 43 24
134 36 38 -42 11 6 16 22 23 34 274 -54 136 28 43 -42 20 25 132 49 1 -42 0 14 140 43 17 -42 34 10 129 13 52 -41 32 49
134 19 9 -43 1 19 16 22 33 34 275 -53 136 12 28 -43 10 52 132 30 20 -42 50 13 140 29 49 -43 25 3 128 52 51 -42 22 18
134 2 47 -43 51 36 16 22 43 34 276 -53 135 57 28 -44 1 21 132 12 40 -43 40 17 140 17 55 -44 15 56 128 32 38 -43 11 52
133 47 35 -44 41 58 16 22 53 35 276 -52 135 43 45 -44 51 54 131 56 3 -44 30 26 140 7 37 -45 6 50 128 13 15 -44 1 33
133 33 34 -45 32 25 16 23 3 35 277 -52 135 31 21 -45 42 32 131 40 30 -45 20 42 139 58 57 -45 57 46 127 54 43 -44 51 21
133 20 47 -46 22 59 16 23 12 35 278 -51 135 20 20 -46 33 16 131 26 3 -46 11 5 139 52 1 -46 48 45 127 37 2 -45 41 17
133 9 16 -47 13 41 16 23 22 35 278 -50 135 10 44 -47 24 7 131 12 44 -47 1 37 139 46 52 -47 39 48 127 20 14 -46 31 24
132 59 5 -48 4 32 16 23 32 34 279 -49 135 2 38 -48 15 6 131 0 37 -47 52 19 139 43 36 -48 30 56 127 4 22 -47 21 40
132 50 19 -48 55 33 16 23 42 34 280 -49 134 56 5 -49 6 13 130 49 44 -48 43 11 139 42 19 -49 22 8 126 49 26 -48 12 9
132 43 0 -49 46 45 16 23 52 34 280 -48 134 51 13 -49 57 30 130 40 9 -49 34 15 139 43 9 -50 13 27 126 35 31 -49 2 50
132 37 16 -50 38 8 16 24 2 34 281 -47 134 48 6 -50 48 58 130 31 57 -50 25 32 139 46 13 -51 4 52 126 22 38 -49 53 46
132 33 11 -51 29 44 16 24 11 34 282 -47 134 46 51 -51 40 37 130 25 14 -51 17 2 139 51 41 -51 56 25 126 10 51 -50 44 56
Uncertainty in time = +/- 19 secs
Prediction of 2009 Jul 29.0
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