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Updated: 2007 JUL 09, 20:57 UT
Event Rank : 94
(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 2007 Aug 06 UT, the 54 km diameter asteroid (584) Semiramis will occult a 11.1 mag star in the constellation Aries for observers along a path beginning just west of Ceduna in South Australia. The path the moves north-east passing near Coober Pedy, before moving into Queensland passing near Winton and Longreach and ending just south of Townsville in morning twilight.
In the case of an occultation, the combined light of the asteroid and the star will drop by 1.4 mag to 12.2 mag (the magnitude of the asteroid) for at most 2.6 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 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
126 55 16 -38 0 0 20 21 22 23 11 -25 127 28 28 126 22 14 127 59 11 125 52 1
127 51 46 -37 0 0 20 21 26 24 10 -24 128 24 51 127 18 52 128 55 27 126 48 46
128 49 1 -36 0 0 20 21 30 25 9 -23 129 22 0 128 16 13 129 52 33 127 46 12
129 47 5 -35 0 0 20 21 34 26 8 -23 130 20 1 129 14 21 130 50 31 128 44 24
130 46 3 -34 0 0 20 21 39 27 8 -22 131 18 58 130 13 20 131 49 27 129 43 25
131 45 59 -33 0 0 20 21 44 28 7 -21 132 18 55 131 13 15 132 49 26 130 43 20
132 46 58 -32 0 0 20 21 48 29 6 -20 133 19 58 132 14 12 133 50 32 131 44 15
133 49 6 -31 0 0 20 21 54 30 5 -19 134 22 11 133 16 14 134 52 51 132 46 13
134 52 28 -30 0 0 20 21 59 31 4 -18 135 25 42 134 19 29 135 56 30 133 49 21
135 57 11 -29 0 0 20 22 5 32 2 -16 136 30 36 135 24 2 137 1 35 134 53 45
137 3 22 -28 0 0 20 22 11 34 1 -15 137 37 1 136 30 0 138 8 14 135 59 32
138 11 8 -27 0 0 20 22 17 35 0 -14 138 45 5 137 37 30 139 16 34 137 6 49
139 20 40 -26 0 0 20 22 23 36 359 -13 139 54 56 138 46 42 140 26 46 138 15 43
140 32 5 -25 0 0 20 22 30 36 357 -12 141 6 46 139 57 44 141 39 0 139 26 25
141 45 35 -24 0 0 20 22 37 37 356 -10 142 20 46 141 10 47 142 53 27 140 39 4
143 1 24 -23 0 0 20 22 44 38 355 -9 143 37 8 142 26 4 144 10 22 141 53 53
144 19 45 -22 0 0 20 22 52 39 353 -7 144 56 8 143 43 47 145 30 0 143 11 4
145 40 55 -21 0 0 20 23 0 40 351 -6 146 18 4 145 4 14 146 52 41 144 30 52
147 5 14 -20 0 0 20 23 9 41 349 -4 147 43 17 146 27 42 148 18 46 145 53 37
148 33 6 -19 0 0 20 23 17 41 348 -3 149 12 12 147 54 35 149 48 42 147 19 38
150 5 0 -18 0 0 20 23 27 42 346 -1 150 45 19 149 25 19 151 23 2 148 49 21
151 41 30 -17 0 0 20 23 36 43 343 1 152 23 17 151 0 26 153 2 26 150 23 16
153 23 20 -16 0 0 20 23 47 43 341 3 154 6 53 152 40 37 154 47 46 152 2 3
155 11 27 -15 0 0 20 23 57 43 339 5 155 57 9 154 26 45 156 40 10 153 46 27
157 7 5 -14 0 0 20 24 9 44 336 7 157 55 28 156 19 56 158 41 10 155 37 32
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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