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Updated: 2011 OCT 13, 18:54 UT
Event Rank : 96
(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 2011 Nov 24 UT, the 61 km diameter asteroid (198) Ampella will occult a 9.2 mag star in the constellation Taurus for observers along a path across Australia beginning near Townsville in Queensland. The path then moves south-west through central Australia, and in Western Australia ends along the south coast, just west of Esperance.
In the case of an occultation, the combined light of the asteroid and the star will drop by 2.3 mag to 11.3 mag (the magnitude of the asteroid) for at most 6.7 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 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
113 55 49 -39 0 0 16 13 13 20 24 -31 113 11 15 114 40 40 112 34 2 115 18 35
115 16 59 -38 0 0 16 13 4 21 23 -32 114 32 28 116 1 48 113 55 19 116 39 41
116 39 5 -37 0 0 16 12 55 23 22 -32 115 54 35 117 23 55 115 17 26 118 1 50
118 2 15 -36 0 0 16 12 45 24 21 -33 117 17 42 118 47 10 116 40 31 119 25 9
119 26 38 -35 0 0 16 12 34 25 20 -34 118 41 58 120 11 41 118 4 42 120 49 49
120 52 23 -34 0 0 16 12 22 27 18 -35 120 7 31 121 37 38 119 30 7 122 15 57
122 19 40 -33 0 0 16 12 10 28 17 -36 121 34 33 123 5 11 120 56 57 123 43 46
123 48 38 -32 0 0 16 11 57 29 16 -37 123 3 12 124 34 31 122 25 21 125 13 25
125 19 31 -31 0 0 16 11 43 31 15 -37 124 33 40 126 5 50 123 55 30 126 45 7
126 52 30 -30 0 0 16 11 28 32 13 -38 126 6 9 127 39 21 125 27 36 128 19 7
128 27 51 -29 0 0 16 11 13 33 12 -39 127 40 55 129 15 21 127 1 53 129 55 40
130 5 51 -28 0 0 16 10 56 34 10 -39 129 18 12 130 54 5 128 38 36 131 35 5
131 46 47 -27 0 0 16 10 39 36 9 -40 130 58 18 132 35 55 130 18 2 133 17 43
133 31 2 -26 0 0 16 10 20 37 7 -40 132 41 34 134 21 13 132 0 32 135 3 57
135 19 3 -25 0 0 16 10 1 38 5 -40 134 28 25 136 10 28 133 46 28 136 54 18
137 11 19 -24 0 0 16 9 40 39 3 -40 136 19 19 138 4 12 135 36 17 138 49 21
139 8 30 -23 0 0 16 9 18 40 1 -40 138 14 52 140 3 7 137 30 34 140 49 50
141 11 20 -22 0 0 16 8 54 41 359 -40 140 15 47 142 8 4 139 29 56 142 56 40
Latitude Latitude Latitude Latitude
142 0 0 -21 37 4 16 8 45 41 358 -40 -21 10 35 -22 3 47 -20 48 31 -22 26 24
143 0 0 -21 9 26 16 8 33 42 357 -40 -20 43 7 -21 35 59 -20 21 11 -21 58 28
144 0 0 -20 42 31 16 8 22 42 356 -40 -20 16 22 -21 8 55 -19 54 33 -21 31 16
145 0 0 -20 16 20 16 8 10 43 354 -40 -19 50 19 -20 42 34 -19 28 39 -21 4 47
146 0 0 -19 50 52 16 7 58 43 353 -39 -19 25 0 -20 16 58 -19 3 27 -20 39 3
147 0 0 -19 26 8 16 7 47 43 352 -39 -19 0 25 -19 52 5 -18 38 58 -20 14 3
148 0 0 -19 2 8 16 7 35 43 351 -39 -18 36 33 -19 27 56 -18 15 13 -19 49 47
149 0 0 -18 38 52 16 7 23 44 350 -39 -18 13 24 -19 4 32 -17 52 10 -19 26 15
150 0 0 -18 16 19 16 7 11 44 348 -38 -17 50 59 -18 41 51 -17 29 52 -19 3 28
151 0 0 -17 54 30 16 6 59 44 347 -38 -17 29 17 -18 19 55 -17 8 16 -18 41 26
152 0 0 -17 33 25 16 6 47 44 346 -37 -17 8 19 -17 58 43 -16 47 24 -18 20 7
153 0 0 -17 13 4 16 6 36 44 345 -37 -16 48 5 -17 38 15 -16 27 15 -17 59 34
Uncertainty in time = +/- 3 secs
Prediction of 2011 Oct 14.0
Use these links for further information:
[Planetary Occultations]
[Using the Predictions]
[Observing Details]
[Timing Details]
[Reporting Details]
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