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Updated: 2011 SEP 12, 03:27 UT
Event Rank : 35
(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 06 UT, the 54 km diameter asteroid (584) Semiramis will occult a 12.7 mag star in the constellation Cancer for observers along a quite uncertain path across Western Australia centred from Carnarvon to Leonora to Caiguna, with Kalgoorlie inside the 1-sigma uncertainty area.
In the case of an occultation, the combined light of the asteroid and the star will drop by 0.8 mag to 12.7 mag (the magnitude of the asteroid) for at most 6.2 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Hugh Harris, 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
131 48 27 -38 0 0 19 5 58 28 20 -10 131 4 56 132 31 18 128 14 49 135 7 15
130 51 29 -37 0 0 19 5 43 28 21 -12 130 7 39 131 34 37 127 16 0 134 11 22
129 52 13 -36 0 0 19 5 28 29 22 -13 129 7 59 130 35 44 126 14 21 133 13 35
128 50 29 -35 0 0 19 5 12 29 24 -14 128 5 43 129 34 28 125 9 36 132 13 46
127 46 3 -34 0 0 19 4 56 30 25 -16 127 0 38 128 30 38 124 1 28 131 11 44
126 38 41 -33 0 0 19 4 38 30 26 -17 125 52 28 127 23 59 122 49 34 130 7 20
125 28 4 -32 0 0 19 4 20 31 28 -18 124 40 53 126 14 16 121 33 26 129 0 20
124 13 50 -31 0 0 19 4 2 31 30 -20 123 25 29 125 1 6 120 12 29 127 50 28
122 55 32 -30 0 0 19 3 42 31 31 -21 122 5 47 123 44 6 118 45 58 126 37 27
121 32 37 -29 0 0 19 3 21 32 33 -23 120 41 7 122 22 45 117 12 54 125 20 53
120 4 20 -28 0 0 19 3 0 32 35 -25 119 10 43 120 56 23 115 31 54 124 0 20
118 29 45 -27 0 0 19 2 37 32 37 -26 117 33 29 119 24 11 113 41 2 122 35 14
116 47 36 -26 0 0 19 2 13 31 38 -28 115 47 56 117 45 3 111 37 22 121 4 52
114 56 6 -25 0 0 19 1 47 31 41 -30 113 51 58 115 57 26 109 16 2 119 28 18
112 52 34 -24 0 0 19 1 20 31 43 -33 111 42 17 113 59 8 106 27 50 117 44 18
Latitude Latitude Latitude Latitude
111 0 0 -23 11 3 19 0 56 30 45 -34 -23 42 0 -22 40 34 -25 43 16 -20 49 57
110 0 0 -22 47 8 19 0 43 29 46 -35 -23 17 46 -22 16 57 -25 17 42 -20 27 20
109 0 0 -22 24 41 19 0 31 29 46 -36 -22 55 3 -21 54 47 -24 53 45 -20 6 7
108 0 0 -22 3 42 19 0 19 29 47 -37 -22 33 48 -21 34 4 -24 31 22 -19 46 16
107 0 0 -21 44 10 19 0 7 28 48 -38 -22 14 0 -21 14 46 -24 10 32 -19 27 47
Uncertainty in time = +/- 12 secs
Prediction of 2011 Aug 5.0
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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