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Updated: 2012 SEP 26, 23:15 UT
Event Rank : 30
(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 Nov 05 UT, the 119 km diameter asteroid (2241) Alcathous will occult a 11.9 mag star in the constellation Pegasus for observers along a north-to-south path across Western Australia beginning near Port Hedland and Derby. The path tracks south passing near Kalgoorlie, before ending over the Nullarbor Plain.
In the case of an occultation, the combined light of the asteroid and the star will drop by 4.5 mag to 16.4 mag (the magnitude of the asteroid) for at most 15.3 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
119 47 32 -10 0 21 13 35 2 53 303 -49 120 25 39 -10 2 14 119 9 40 - 9 58 34 123 17 40 -10 11 45 116 25 16 - 9 51 48
119 57 27 -11 23 34 13 35 20 52 305 -48 120 35 53 -11 25 30 119 19 18 -11 21 43 123 29 24 -11 35 18 116 33 41 -11 14 45
120 8 53 -12 47 41 13 35 38 51 306 -47 120 47 41 -12 49 40 119 30 24 -12 45 47 123 42 53 -12 59 48 116 43 23 -12 38 34
120 21 57 -14 12 47 13 35 56 50 307 -47 121 1 9 -14 14 51 119 43 4 -14 10 49 123 58 17 -14 25 20 116 54 29 -14 3 20
120 36 47 -15 38 59 13 36 14 49 308 -46 121 16 25 -15 41 8 119 57 28 -15 36 56 124 15 46 -15 52 1 117 7 6 -15 29 9
120 53 32 -17 6 22 13 36 32 48 309 -45 121 33 41 -17 8 36 120 13 43 -17 4 14 124 35 30 -17 19 56 117 21 20 -16 56 7
121 12 23 -18 35 4 13 36 51 47 310 -44 121 53 7 -18 37 24 120 32 1 -18 32 50 124 57 45 -18 49 15 117 37 22 -18 24 20
121 33 34 -20 5 11 13 37 9 45 310 -44 122 14 57 -20 7 39 120 52 34 -20 2 51 125 22 46 -20 20 5 117 55 21 -19 53 56
121 57 21 -21 36 55 13 37 27 44 311 -43 122 39 28 -21 39 30 121 15 38 -21 34 27 125 50 54 -21 52 35 118 15 32 -21 25 2
122 24 1 -23 10 23 13 37 45 43 312 -42 123 6 59 -23 13 7 121 41 30 -23 7 47 126 22 33 -23 26 58 118 38 8 -22 57 49
122 53 59 -24 45 48 13 38 3 41 312 -41 123 37 54 -24 48 42 122 10 32 -24 43 2 126 58 13 -25 3 26 119 3 28 -24 32 26
123 27 42 -26 23 23 13 38 21 40 313 -40 124 12 43 -26 26 29 122 43 12 -26 20 26 127 38 30 -26 42 14 119 31 53 -26 9 7
124 5 45 -28 3 24 13 38 39 38 313 -39 124 52 2 -28 6 45 123 20 1 -28 0 14 128 24 12 -28 23 41 120 3 52 -27 48 5
124 48 52 -29 46 11 13 38 57 36 313 -38 125 36 38 -29 49 48 124 1 43 -29 42 45 129 16 19 -30 8 9 120 39 57 -29 29 37
125 37 59 -31 32 5 13 39 16 35 313 -37 126 27 30 -31 36 2 124 49 10 -31 28 21 130 16 8 -31 56 6 121 20 51 -31 14 3
126 34 20 -33 21 36 13 39 34 33 313 -36 127 25 57 -33 25 56 125 43 31 -33 17 30 131 25 29 -33 48 7 122 7 28 -33 1 48
127 39 34 -35 15 20 13 39 52 31 313 -34 128 33 45 -35 20 9 126 46 20 -35 10 46 132 46 49 -35 44 59 123 0 59 -34 53 21
128 55 58 -37 14 2 13 40 10 29 313 -33 129 53 22 -37 19 29 127 59 44 -37 8 53 134 23 48 -37 47 45 124 2 59 -36 49 21
130 26 53 -39 18 48 13 40 28 26 312 -32 131 28 27 -39 25 4 129 26 47 -39 12 54 136 22 6 -39 57 59 125 15 42 -38 50 38
132 17 23 -41 31 7 13 40 46 24 311 -30 133 24 36 -41 38 31 131 12 6 -41 24 12 138 51 24 -42 18 9 126 42 20 -40 58 17
Uncertainty in time = +/- 34 secs
Prediction of 2012 Sep 27.0
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