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Updated: 2010 JUL 08, 11:32 UT
Event Rank : 68
(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 2010 Aug 07 UT, the 54 km diameter asteroid (925) Alphonsina will occult a 9.1 mag star in the constellation Scorpius for observers along a south-to-north path across Western Australia from Esperance to Karratha.
In the case of an occultation, the combined light of the asteroid and the star will drop by 4.1 mag to 13.2 mag (the magnitude of the asteroid) for at most 5.6 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
122 28 55 -35 10 59 14 51 52 53 257 -66 122 7 58 -35 16 51 122 49 54 -35 5 2 121 32 0 -35 26 45 123 26 5 -34 54 39
121 54 2 -34 5 58 14 52 6 53 256 -67 121 33 20 -34 11 44 122 14 46 -34 0 7 120 57 49 -34 21 29 122 50 31 -33 49 53
121 21 11 -33 0 33 14 52 19 53 255 -67 121 0 43 -33 6 14 121 41 40 -32 54 47 120 25 36 -33 15 51 122 17 1 -32 44 42
120 50 14 -31 54 45 14 52 32 53 253 -68 120 30 0 -32 0 22 121 10 30 -31 49 4 119 55 17 -32 9 51 121 45 28 -31 39 6
120 21 6 -30 48 32 14 52 45 53 252 -68 120 1 5 -30 54 5 120 41 10 -30 42 55 119 26 44 -31 3 27 121 15 46 -30 33 5
119 53 42 -29 41 55 14 52 59 53 251 -69 119 33 53 -29 47 25 120 13 34 -29 36 22 118 59 53 -29 56 41 120 47 50 -29 26 38
119 27 58 -28 34 53 14 53 12 53 249 -69 119 8 19 -28 40 19 119 47 38 -28 29 22 118 34 39 -28 49 30 120 21 35 -28 19 44
119 3 47 -27 27 24 14 53 25 53 248 -69 118 44 20 -27 32 47 119 23 18 -27 21 56 118 10 57 -27 41 53 119 56 57 -27 12 22
118 41 8 -26 19 27 14 53 39 53 247 -69 118 21 50 -26 24 49 119 0 29 -26 14 2 117 48 45 -26 33 51 119 33 51 -26 4 32
118 19 57 -25 11 2 14 53 52 53 245 -70 118 0 48 -25 16 22 118 39 8 -25 5 39 117 27 58 -25 25 21 119 12 15 -24 56 12
118 0 10 -24 2 7 14 54 5 53 244 -70 117 41 9 -24 7 25 118 19 13 -23 56 45 117 8 34 -24 16 22 118 52 6 -23 47 21
117 41 45 -22 52 41 14 54 19 52 242 -70 117 22 52 -22 57 58 118 0 40 -22 47 20 116 50 31 -23 6 53 118 33 20 -22 37 57
117 24 40 -21 42 41 14 54 32 52 241 -70 117 5 54 -21 47 57 117 43 28 -21 37 20 116 33 45 -21 56 51 118 15 57 -21 27 59
117 8 53 -20 32 6 14 54 45 51 240 -70 116 50 13 -20 37 22 117 27 35 -20 26 45 116 18 15 -20 46 15 117 59 53 -20 17 24
116 54 22 -19 20 53 14 54 59 51 238 -70 116 35 48 -19 26 10 117 12 59 -19 15 33 116 3 59 -19 35 3 117 45 7 -19 6 11
116 41 7 -18 9 1 14 55 12 50 237 -70 116 22 38 -18 14 18 116 59 39 -18 3 40 115 50 58 -18 23 13 117 31 39 -17 54 17
116 29 6 -16 56 27 14 55 25 50 236 -70 116 10 41 -17 1 45 116 47 34 -16 51 4 115 39 8 -17 10 42 117 19 28 -16 41 39
116 18 19 -15 43 7 14 55 39 49 235 -70 115 59 58 -15 48 27 116 36 44 -15 37 43 115 28 31 -15 57 26 117 8 32 -15 28 15
116 8 46 -14 29 0 14 55 52 49 233 -69 115 50 27 -14 34 22 116 27 9 -14 23 34 115 19 5 -14 43 25 116 58 53 -14 14 2
116 0 28 -13 14 1 14 56 5 48 232 -69 115 42 10 -13 19 26 116 18 48 -13 8 32 115 10 52 -13 28 33 116 50 30 -12 58 55
Uncertainty in time = +/- 5 secs
Prediction of 2010 Jul 8.0
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