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Updated: 2012 MAR 20, 20:12 UT
Event Rank : 9
(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 2012 May 18 UT, the 16 km diameter asteroid (8369) 1991 GR will occult a 10.4 mag star in the constellation Scorpius for observers along a path across Papua New Guinea.
In the case of an occultation, the combined light of the asteroid and the star will drop by 5.3 mag to 15.7 mag (the magnitude of the asteroid) for at most 1.3 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Hugh Harris, 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 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
166 6 47 9 0 0 15 9 48 37 196 -46 165 58 11 166 15 22 163 48 33 168 20 7
164 52 18 8 0 0 15 9 59 39 195 -47 164 43 33 165 1 2 162 31 26 167 7 52
163 35 21 7 0 0 15 10 11 40 194 -49 163 26 25 163 44 14 161 11 32 165 53 25
162 15 40 6 0 0 15 10 23 41 193 -50 162 6 33 162 24 45 159 48 31 164 36 33
160 53 0 5 0 0 15 10 36 42 192 -52 160 43 39 161 2 18 158 22 3 163 17 4
159 27 0 4 0 0 15 10 49 44 191 -54 159 17 25 159 36 34 156 51 45 161 54 40
157 57 20 3 0 0 15 11 3 45 189 -55 157 47 27 158 7 10 155 17 7 160 29 5
156 23 30 2 0 0 15 11 18 46 188 -57 156 13 18 156 33 40 153 37 34 158 59 56
154 44 59 1 0 0 15 11 33 47 186 -59 154 34 24 154 55 31 151 52 20 157 26 47
153 1 5 0 0 0 15 11 50 48 185 -61 152 50 4 153 12 4 150 0 31 155 49 9
151 10 57 - 1 0 0 15 12 7 49 183 -63 150 59 24 151 22 27 148 0 51 154 6 23
Latitude Latitude Latitude Latitude
150 0 0 - 1 36 44 15 12 19 50 182 -64 - 1 30 41 - 1 42 46 - 0 0 16 - 3 11 1
149 0 0 - 2 6 38 15 12 28 51 180 -65 - 2 0 38 - 2 12 37 - 0 30 53 - 3 40 14
148 0 0 - 2 35 28 15 12 38 51 179 -66 - 2 29 31 - 2 41 25 - 1 0 25 - 4 8 27
147 0 0 - 3 3 17 15 12 47 52 178 -67 - 2 57 22 - 3 9 11 - 1 28 52 - 4 35 38
146 0 0 - 3 30 3 15 12 57 52 177 -68 - 3 24 11 - 3 35 55 - 1 56 17 - 5 1 50
145 0 0 - 3 55 49 15 13 7 52 176 -69 - 3 49 59 - 4 1 39 - 2 22 39 - 5 27 1
144 0 0 - 4 20 34 15 13 16 53 175 -70 - 4 14 46 - 4 26 22 - 2 47 58 - 5 51 14
143 0 0 - 4 44 20 15 13 26 53 173 -71 - 4 38 34 - 4 50 5 - 3 12 17 - 6 14 29
142 0 0 - 5 7 6 15 13 35 53 172 -72 - 5 1 22 - 5 12 50 - 3 35 35 - 6 36 46
141 0 0 - 5 28 54 15 13 44 53 171 -73 - 5 23 12 - 5 34 36 - 3 57 52 - 6 58 6
140 0 0 - 5 49 44 15 13 54 54 170 -73 - 5 44 3 - 5 55 24 - 4 19 11 - 7 18 29
139 0 0 - 6 9 36 15 14 3 54 168 -74 - 6 3 58 - 6 15 15 - 4 39 30 - 7 37 56
138 0 0 - 6 28 32 15 14 13 54 167 -75 - 6 22 55 - 6 34 9 - 4 58 52 - 7 56 27
137 0 0 - 6 46 31 15 14 22 54 166 -76 - 6 40 56 - 6 52 7 - 5 17 15 - 8 14 4
136 0 0 - 7 3 35 15 14 31 54 164 -76 - 6 58 0 - 7 9 9 - 5 34 42 - 8 30 46
135 0 0 - 7 19 43 15 14 40 54 163 -77 - 7 14 10 - 7 25 16 - 5 51 11 - 8 46 33
134 0 0 - 7 34 56 15 14 50 54 162 -77 - 7 29 24 - 7 40 27 - 6 6 44 - 9 1 27
133 0 0 - 7 49 14 15 14 59 54 161 -78 - 7 43 44 - 7 54 45 - 6 21 22 - 9 15 28
132 0 0 - 8 2 39 15 15 8 54 160 -78 - 7 57 9 - 8 8 8 - 6 35 4 - 9 28 36
131 0 0 - 8 15 9 15 15 17 54 158 -78 - 8 9 41 - 8 20 38 - 6 47 51 - 9 40 51
130 0 0 - 8 26 47 15 15 26 53 157 -79 - 8 21 19 - 8 32 14 - 6 59 43 - 9 52 14
129 0 0 - 8 37 31 15 15 35 53 156 -79 - 8 32 4 - 8 42 57 - 7 10 41 -10 2 44
128 0 0 - 8 47 22 15 15 44 53 155 -79 - 8 41 56 - 8 52 47 - 7 20 45 -10 12 23
127 0 0 - 8 56 20 15 15 52 53 154 -79 - 8 50 55 - 9 1 45 - 7 29 55 -10 21 11
126 0 0 - 9 4 26 15 16 1 52 153 -79 - 8 59 2 - 9 9 51 - 7 38 12 -10 29 8
125 0 0 - 9 11 41 15 16 10 52 152 -78 - 9 6 16 - 9 17 4 - 7 45 35 -10 36 13
124 0 0 - 9 18 3 15 16 19 52 151 -78 - 9 12 39 - 9 23 26 - 7 52 5 -10 42 28
123 0 0 - 9 23 33 15 16 27 51 150 -78 - 9 18 10 - 9 28 56 - 7 57 42 -10 47 51
122 0 0 - 9 28 12 15 16 36 51 149 -77 - 9 22 49 - 9 33 34 - 8 2 26 -10 52 25
121 0 0 - 9 31 59 15 16 44 50 148 -77 - 9 26 36 - 9 37 21 - 8 6 18 -10 56 8
120 0 0 - 9 34 54 15 16 53 50 147 -76 - 9 29 32 - 9 40 16 - 8 9 17 -10 59 0
119 0 0 - 9 36 59 15 17 1 49 147 -75 - 9 31 36 - 9 42 20 - 8 11 23 -11 1 2
118 0 0 - 9 38 11 15 17 9 49 146 -75 - 9 32 49 - 9 43 33 - 8 12 37 -11 2 14
117 0 0 - 9 38 33 15 17 18 48 145 -74 - 9 33 11 - 9 43 55 - 8 12 58 -11 2 36
116 0 0 - 9 38 3 15 17 26 48 144 -73 - 9 32 40 - 9 43 24 - 8 12 27 -11 2 7
115 0 0 - 9 36 41 15 17 34 47 144 -72 - 9 31 19 - 9 42 3 - 8 11 3 -11 0 47
114 0 0 - 9 34 28 15 17 42 47 143 -72 - 9 29 5 - 9 39 50 - 8 8 46 -10 58 38
113 0 0 - 9 31 23 15 17 50 46 143 -71 - 9 26 0 - 9 36 45 - 8 5 36 -10 55 37
112 0 0 - 9 27 26 15 17 58 45 142 -70 - 9 22 3 - 9 32 49 - 8 1 33 -10 51 46
111 0 0 - 9 22 37 15 18 5 45 141 -69 - 9 17 14 - 9 28 1 - 7 56 37 -10 47 4
110 0 0 - 9 16 56 15 18 13 44 141 -68 - 9 11 32 - 9 22 20 - 7 50 48 -10 41 31
109 0 0 - 9 10 23 15 18 21 43 140 -67 - 9 4 58 - 9 15 47 - 7 44 5 -10 35 7
108 0 0 - 9 2 56 15 18 28 43 140 -67 - 8 57 31 - 9 8 22 - 7 36 27 -10 27 51
107 0 0 - 8 54 37 15 18 36 42 140 -66 - 8 49 11 - 9 0 3 - 7 27 56 -10 19 43
Uncertainty in time = +/- 15 secs
Prediction of 2012 Jan 10.0
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