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Updated: 2009 APR 15, 19:23 UT
Event Rank : 72
(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 2009 Apr 21 UT, the 86 km diameter asteroid (494) Virtus will occult a 12.2 mag star in the constellation Sagittarius for observers along a path running down the east coast of Australia, passing over Rockhampton, near Brisbane and over Newcastle and Sydney.
In the case of an occultation, the combined light of the asteroid and the star will drop by 1.8 mag to 13.8 mag (the magnitude of the asteroid) for at most 20.4 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
146 58 44 -10 57 53 15 20 37 46 120 -73 147 27 4 -10 55 18 146 30 11 -11 0 18 148 12 34 -10 50 49 145 43 31 -11 3 53
147 25 57 -12 21 7 15 21 11 48 119 -72 147 54 15 -12 18 23 146 57 27 -12 23 41 148 39 41 -12 13 39 146 10 53 -12 27 33
147 51 38 -13 43 13 15 21 44 49 118 -72 148 19 55 -13 40 21 147 23 10 -13 45 57 149 5 21 -13 35 23 146 36 37 -13 50 3
148 15 56 -15 4 19 15 22 17 50 117 -71 148 44 14 -15 1 19 147 47 26 -15 7 12 149 29 43 -14 56 8 147 0 53 -15 11 32
148 38 56 -16 24 31 15 22 51 51 115 -70 149 7 18 -16 21 23 148 10 24 -16 27 31 149 52 51 -16 16 0 147 23 47 -16 32 4
149 0 45 -17 43 54 15 23 24 52 114 -70 149 29 11 -17 40 38 148 32 9 -17 47 1 150 14 52 -17 35 3 147 45 25 -17 51 47
149 21 28 -19 2 32 15 23 57 53 113 -69 149 50 0 -18 59 9 148 52 46 -19 5 46 150 35 51 -18 53 24 148 5 52 -19 10 43
149 41 9 -20 20 30 15 24 31 54 111 -68 150 9 49 -20 17 1 149 12 19 -20 23 51 150 55 52 -20 11 5 148 25 14 -20 28 59
149 59 53 -21 37 52 15 25 4 54 109 -67 150 28 41 -21 34 17 149 30 54 -21 41 20 151 14 59 -21 28 11 148 43 34 -21 46 38
150 17 42 -22 54 43 15 25 37 55 108 -66 150 46 40 -22 51 1 149 48 32 -22 58 16 151 33 15 -22 44 46 149 0 55 -23 3 45
150 34 39 -24 11 5 15 26 11 56 106 -65 151 3 50 -24 7 18 150 5 18 -24 14 44 151 50 44 -24 0 53 149 17 22 -24 20 22
150 50 49 -25 27 2 15 26 44 57 104 -65 151 20 13 -25 23 9 150 21 14 -25 30 47 152 7 28 -25 16 35 149 32 56 -25 36 34
151 6 12 -26 42 37 15 27 17 57 102 -64 151 35 51 -26 38 39 150 36 22 -26 46 28 152 23 30 -26 31 56 149 47 40 -26 52 24
151 20 51 -27 57 53 15 27 51 58 100 -63 151 50 46 -27 53 49 150 50 45 -28 1 49 152 38 51 -27 46 58 150 1 36 -28 7 54
151 34 48 -29 12 53 15 28 24 58 98 -62 152 5 1 -29 8 44 151 4 24 -29 16 55 152 53 35 -29 1 45 150 14 45 -29 23 8
151 48 5 -30 27 40 15 28 58 59 96 -61 152 18 37 -30 23 26 151 17 21 -30 31 47 153 7 42 -30 16 18 150 27 10 -30 38 8
152 0 42 -31 42 17 15 29 31 59 94 -60 152 31 35 -31 37 58 151 29 37 -31 46 28 153 21 14 -31 30 41 150 38 51 -31 52 58
152 12 41 -32 56 45 15 30 4 60 91 -59 152 43 57 -32 52 21 151 41 13 -33 1 1 153 34 12 -32 44 56 150 49 49 -33 7 39
152 24 3 -34 11 8 15 30 38 60 89 -58 152 55 44 -34 6 39 151 52 10 -34 15 29 153 46 38 -33 59 6 151 0 6 -34 22 15
152 34 49 -35 25 28 15 31 11 60 87 -57 153 6 56 -35 20 54 152 2 29 -35 29 54 153 58 33 -35 13 13 151 9 40 -35 36 47
152 44 58 -36 39 48 15 31 44 60 84 -56 153 17 34 -36 35 9 152 12 10 -36 44 19 154 9 57 -36 27 20 151 18 33 -36 51 19
152 54 32 -37 54 10 15 32 18 60 82 -55 153 27 39 -37 49 26 152 21 12 -37 58 45 154 20 50 -37 41 28 151 26 45 -38 5 53
153 3 30 -39 8 36 15 32 51 60 80 -54 153 37 10 -39 3 47 152 29 37 -39 13 16 154 31 14 -38 55 41 151 34 14 -39 20 32
153 11 52 -40 23 9 15 33 24 60 77 -53 153 46 8 -40 18 15 152 37 23 -40 27 54 154 41 8 -40 10 1 151 41 0 -40 35 17
153 19 38 -41 37 51 15 33 58 60 75 -52 153 54 31 -41 32 53 152 44 29 -41 42 41 154 50 33 -41 24 31 151 47 3 -41 50 12
153 26 46 -42 52 46 15 34 31 60 73 -51 154 2 21 -42 47 42 152 50 56 -42 57 41 154 59 28 -42 39 12 151 52 21 -43 5 19
153 33 16 -44 7 55 15 35 4 60 70 -50 154 9 36 -44 2 46 152 56 41 -44 12 55 155 7 54 -43 54 7 151 56 51 -44 20 40
Uncertainty in time = +/- 17 secs
Prediction of 2009 Apr 16.0
Use these links for further information:
[Planetary Occultations]
[Using the Predictions]
[Observing Details]
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