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Updated: 2011 OCT 13, 17:17 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 2011 Nov 03 UT, the 61 km diameter asteroid (198) Ampella will occult a 12.2 mag star in the constellation Taurus for observers along a path across central Australia in morning twilight and passing near Eucla in Western Australia.
In the case of an occultation, the combined light of the asteroid and the star will drop by 0.5 mag to 11.7 mag (the magnitude of the asteroid) for at most 19.2 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
122 3 26 -41 0 0 19 48 5 20 348 -9 121 20 15 122 47 5 120 31 33 123 37 26
122 36 11 -40 0 0 19 47 43 21 348 -9 121 53 15 123 19 33 121 4 52 124 9 36
123 10 38 -39 0 0 19 47 20 22 347 -9 122 27 56 123 53 47 121 39 49 124 43 34
123 46 48 -38 0 0 19 46 56 22 346 -10 123 4 18 124 29 47 122 16 23 125 19 22
124 24 43 -37 0 0 19 46 30 23 346 -10 123 42 21 125 7 33 122 54 36 125 56 59
125 4 21 -36 0 0 19 46 4 24 345 -10 124 22 5 125 47 6 123 34 27 126 36 26
125 45 46 -35 0 0 19 45 36 25 345 -10 125 3 33 126 28 28 124 16 0 127 17 45
126 28 59 -34 0 0 19 45 7 26 344 -10 125 46 46 127 11 40 124 59 14 128 0 58
127 14 1 -33 0 0 19 44 37 27 343 -10 126 31 47 127 56 46 125 44 13 128 46 8
128 0 57 -32 0 0 19 44 5 27 342 -10 127 18 37 128 43 47 126 30 58 129 33 17
128 49 48 -31 0 0 19 43 33 28 342 -10 128 7 21 129 32 47 127 19 33 130 22 28
129 40 39 -30 0 0 19 42 59 29 341 -9 128 58 1 130 23 51 128 10 2 131 13 47
130 33 35 -29 0 0 19 42 23 30 340 -9 129 50 42 131 17 2 129 2 28 132 7 18
131 28 40 -28 0 0 19 41 47 30 339 -9 130 45 29 132 12 27 129 56 57 133 3 6
132 26 1 -27 0 0 19 41 9 31 338 -9 131 42 28 133 10 11 130 53 32 134 1 19
133 25 44 -26 0 0 19 40 30 32 337 -8 132 41 46 134 10 22 131 52 22 135 2 5
134 27 58 -25 0 0 19 39 49 32 336 -8 133 43 29 135 13 9 132 53 33 136 5 32
135 32 52 -24 0 0 19 39 7 33 335 -8 134 47 47 136 18 41 133 57 13 137 11 51
136 40 37 -23 0 0 19 38 23 33 334 -7 135 54 50 137 27 11 135 3 31 138 21 15
137 51 26 -22 0 0 19 37 37 34 332 -7 137 4 50 138 38 51 136 12 40 139 33 59
139 5 33 -21 0 0 19 36 50 34 331 -6 138 18 1 139 53 58 137 24 52 140 50 20
140 23 16 -20 0 0 19 36 1 35 330 -5 139 34 40 141 12 51 138 40 22 142 10 40
141 44 58 -19 0 0 19 35 10 35 328 -5 140 55 6 142 35 54 139 59 28 143 35 24
143 11 3 -18 0 0 19 34 17 35 327 -4 142 19 43 144 3 36 141 22 32 145 5 4
144 42 5 -17 0 0 19 33 22 35 325 -3 143 49 0 145 36 31 142 50 1 146 40 21
Uncertainty in time = +/- 11 secs
Prediction of 2011 Oct 14.0
Use these links for further information:
[Planetary Occultations]
[Using the Predictions]
[Observing Details]
[Timing Details]
[Reporting Details]
[Report Form]
[Asteroid Occultation Results]
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