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Updated: 2011 JUL 21, 22:23 UT
Event Rank : 71
(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 Aug 19 UT, the 63 km diameter asteroid (487) Venetia will occult a 12.8 mag star in the constellation Sagittarius for observers along a path passing near Geraldton and Moora in Western Australia.
In the case of an occultation, the combined light of the asteroid and the star will drop by 0.6 mag to 12.4 mag (the magnitude of the asteroid) for at most 10.5 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Alice Monet, TMO astrometry for the asteroid kindly provided by Bill Owen, 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
133 41 23 -16 27 33 18 30 4 5 247 -41 137 4 45 -15 12 38 131 42 46 -17 4 23 ... .. .. .. .. .. 129 17 15 -17 42 58
129 38 40 -18 50 11 18 30 21 10 248 -45 131 5 25 -18 27 51 128 22 10 -19 7 50 134 8 10 -17 32 33 126 32 38 -19 29 53
126 57 48 -20 35 47 18 30 38 13 249 -48 128 5 18 -20 22 21 125 55 7 -20 47 1 130 8 55 -19 54 3 124 21 26 -21 1 35
124 49 3 -22 6 46 18 30 55 15 250 -49 125 47 26 -21 57 39 123 53 41 -22 14 29 127 30 2 -21 39 11 122 29 18 -22 24 33
122 58 49 -23 29 17 18 31 12 17 251 -51 123 51 42 -23 22 51 122 8 5 -23 34 43 125 22 51 -23 9 54 120 49 52 -23 41 40
121 21 0 -24 46 6 18 31 29 19 252 -52 122 10 11 -24 41 33 120 33 29 -24 49 53 123 34 0 -24 32 15 119 19 41 -24 54 32
119 52 15 -25 58 46 18 31 46 20 253 -53 120 38 46 -25 55 37 119 7 6 -26 1 17 121 57 27 -25 48 58 117 56 36 -26 4 7
118 30 28 -27 8 13 18 32 3 22 253 -54 119 15 0 -27 6 11 117 47 7 -27 9 43 120 29 53 -27 1 34 116 39 11 -27 11 6
117 14 17 -28 15 8 18 32 20 23 254 -54 117 57 15 -28 13 59 116 32 20 -28 15 47 119 9 16 -28 11 1 115 26 24 -28 15 56
116 2 41 -29 19 56 18 32 37 24 255 -55 116 44 26 -29 19 33 115 21 51 -29 19 54 117 54 12 -29 17 57 114 17 30 -29 19 0
114 54 56 -30 23 0 18 32 54 25 256 -55 115 35 43 -30 23 16 114 14 59 -30 22 21 116 43 42 -30 22 48 113 11 56 -30 20 32
113 50 29 -31 24 35 18 33 11 27 257 -56 114 30 29 -31 25 24 113 11 15 -31 23 24 115 37 3 -31 25 57 112 9 15 -31 20 47
112 48 54 -32 24 53 18 33 29 28 258 -56 113 28 17 -32 26 13 112 10 14 -32 23 14 114 33 42 -32 27 37 111 9 4 -32 19 54
111 49 49 -33 24 6 18 33 46 28 259 -56 112 28 42 -33 25 52 111 11 37 -33 22 1 113 33 13 -33 28 3 110 11 6 -33 18 1
110 52 57 -34 22 21 18 34 3 29 260 -56 111 31 27 -34 24 31 110 15 6 -34 19 52 112 35 15 -34 27 24 109 15 6 -34 15 17
109 58 4 -35 19 45 18 34 20 30 261 -56 110 36 15 -35 22 18 109 20 30 -35 16 55 111 39 31 -35 25 49 108 20 53 -35 11 48
109 4 58 -36 16 25 18 34 37 31 262 -56 109 42 56 -36 19 18 108 27 35 -36 13 16 110 45 47 -36 23 24 107 28 16 -36 7 38
108 13 28 -37 12 26 18 34 54 32 263 -56 108 51 17 -37 15 38 107 36 14 -37 8 58 109 53 51 -37 20 16 106 37 6 -37 2 52
107 23 26 -38 7 52 18 35 11 32 264 -56 108 1 10 -38 11 22 106 46 17 -38 4 7 109 3 33 -38 16 29 105 47 14 -37 57 34
106 34 45 -39 2 47 18 35 28 33 265 -56 107 12 27 -39 6 34 105 57 37 -38 58 47 108 14 45 -39 12 9 104 58 36 -38 51 48
Uncertainty in time = +/- 9 secs
Prediction of 2011 Jul 22.0
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