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Updated: 2006 MAR 14, 03:09 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 2006 Mar 21 UT, the 116 km diameter asteroid (909) Ulla will occult a 10.8 mag star in the constellation Leo for observers along a moderately wide path across south-western Western Australia. The shadow passes directly over Perth soon after evening twilight.
In the case of an occultation, the combined light of the asteroid and the star will drop by 3.8 mag to 14.6 mag (the magnitude of the asteroid) for at most 8.6 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Ron Stone, 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
134 7 3 -45 0 0 11 8 33 20 40 -21 136 22 21 131 42 23 138 20 5 129 18 49
133 18 50 -44 0 0 11 8 41 20 41 -20 135 34 47 130 53 7 137 32 52 128 28 2
132 26 41 -43 0 0 11 8 51 21 42 -20 134 43 42 129 59 22 136 42 27 127 32 7
131 30 23 -42 0 0 11 9 0 21 43 -20 133 48 56 129 0 52 135 48 41 126 30 39
130 29 39 -41 0 0 11 9 10 21 44 -20 132 50 16 127 57 12 134 51 25 125 23 5
129 24 7 -40 0 0 11 9 21 21 45 -19 131 47 26 126 47 51 133 50 25 124 8 37
128 13 17 -39 0 0 11 9 32 21 46 -18 130 40 3 125 32 7 132 45 24 122 46 12
126 56 31 -38 0 0 11 9 43 21 48 -18 129 27 41 124 9 2 131 36 0 121 14 14
125 32 57 -37 0 0 11 9 55 21 49 -17 128 9 42 122 37 13 130 21 47 119 30 21
124 1 24 -36 0 0 11 10 8 21 50 -16 126 45 21 120 54 41 129 2 9 117 30 39
122 20 9 -35 0 0 11 10 21 21 52 -15 125 13 31 118 58 15 127 36 21 115 7 55
120 26 38 -34 0 0 11 10 35 20 54 -14 123 32 42 116 42 29 126 3 20 112 5 40
118 16 36 -33 0 0 11 10 51 19 55 -12 121 40 41 113 56 19 124 21 40 107 17 22
117 0 0 -32 28 45 11 10 59 19 57 -11 -30 57 41 -34 7 10 -29 39 5 -35 46 6
116 0 0 -32 6 19 11 11 5 18 57 -10 -30 36 22 -33 43 18 -29 18 38 -35 20 31
115 0 0 -31 45 36 11 11 12 18 58 -9 -30 16 41 -33 21 19 -28 59 43 -34 57 1
114 0 0 -31 26 36 11 11 18 17 59 -9 -29 58 35 -33 1 11 -28 42 19 -34 35 33
113 0 0 -31 9 16 11 11 23 16 59 -8 -29 42 3 -32 42 50 -28 26 25 -34 16 2
112 0 0 -30 53 34 11 11 29 16 60 -7 -29 27 4 -32 26 15 -28 11 58 -33 58 25
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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