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Updated: 2011 APR 16, 15:05 UT
Event Rank : 14
(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 Jun 05 UT, the 28 km diameter asteroid (16785) 1997 AL1 will occult a 10.4 mag star in the constellation Capricornus for observers along a very narrow, uncertain path across Australia, from Ingham across Queensland and South Australia to Adelaide, and across New Guinea near Baniara.
In the case of an occultation, the combined light of the asteroid and the star will drop by 6.7 mag to 17.1 mag (the magnitude of the asteroid) for at most 4.0 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
150 51 14 - 3 0 0 17 59 45 77 143 -28 150 59 9 150 43 19 152 14 26 149 27 37
150 36 27 - 4 0 0 17 59 29 77 139 -28 150 44 23 150 28 31 151 59 49 149 12 38
150 21 24 - 5 0 0 17 59 12 78 135 -29 150 29 21 150 13 27 151 44 59 148 57 22
150 6 3 - 6 0 0 17 58 56 78 131 -30 150 14 2 149 58 5 151 29 53 148 41 46
149 50 25 - 7 0 0 17 58 39 78 126 -30 149 58 25 149 42 25 151 14 31 148 25 50
149 34 27 - 8 0 0 17 58 23 79 121 -31 149 42 29 149 26 25 150 58 51 148 9 33
149 18 10 - 9 0 0 17 58 6 79 116 -32 149 26 13 149 10 6 150 42 54 147 52 54
149 1 31 -10 0 0 17 57 49 79 111 -32 149 9 37 148 53 25 150 26 37 147 35 52
148 44 29 -11 0 0 17 57 32 79 105 -33 148 52 38 148 36 21 150 10 0 147 18 25
148 27 4 -12 0 0 17 57 16 79 100 -34 148 35 15 148 18 53 149 53 1 147 0 33
148 9 14 -13 0 0 17 56 59 79 95 -34 148 17 28 148 1 1 149 35 40 146 42 13
147 50 58 -14 0 0 17 56 42 78 90 -35 147 59 15 147 42 42 149 17 55 146 23 24
147 32 14 -15 0 0 17 56 25 78 85 -36 147 40 34 147 23 54 148 59 44 146 4 6
147 13 1 -16 0 0 17 56 8 77 81 -36 147 21 25 147 4 38 148 41 6 145 44 16
146 53 18 -17 0 0 17 55 51 77 77 -37 147 1 45 146 44 51 148 22 1 145 23 52
146 33 2 -18 0 0 17 55 35 76 74 -38 146 41 32 146 24 31 148 2 25 145 2 54
146 12 11 -19 0 0 17 55 18 75 71 -38 146 20 46 146 3 36 147 42 19 144 41 18
145 50 45 -20 0 0 17 55 1 75 68 -39 145 59 25 145 42 5 147 21 39 144 19 4
145 28 41 -21 0 0 17 54 44 74 65 -40 145 37 25 145 19 56 147 0 23 143 56 8
145 5 57 -22 0 0 17 54 27 73 63 -40 145 14 46 144 57 7 146 38 31 143 32 29
144 42 30 -23 0 0 17 54 11 72 61 -41 144 51 25 144 33 35 146 16 0 143 8 4
144 18 19 -24 0 0 17 53 54 71 59 -41 144 27 19 144 9 18 145 52 48 142 42 51
143 53 20 -25 0 0 17 53 37 71 58 -42 144 2 26 143 44 13 145 28 52 142 16 47
143 27 32 -26 0 0 17 53 21 70 56 -43 143 36 44 143 18 18 145 4 10 141 49 49
143 0 50 -27 0 0 17 53 4 69 55 -43 143 10 10 142 51 30 144 38 39 141 21 54
142 33 13 -28 0 0 17 52 47 68 54 -44 142 42 39 142 23 45 144 12 16 140 52 58
142 4 36 -29 0 0 17 52 31 67 53 -44 142 14 10 141 55 0 143 44 59 140 22 57
141 34 55 -30 0 0 17 52 14 66 52 -45 141 44 38 141 25 12 143 16 43 139 51 48
141 4 8 -31 0 0 17 51 58 65 51 -45 141 14 0 140 54 16 142 47 25 139 19 27
Latitude Latitude Latitude Latitude
140 0 0 -32 58 5 17 51 26 63 50 -46 -33 16 5 -32 40 2 -36 4 57 -29 44 26
139 0 0 -34 40 47 17 50 58 61 50 -47 -34 58 4 -34 23 25 -37 40 31 -31 34 58
138 0 0 -36 16 38 17 50 32 59 49 -48 -36 33 18 -35 59 56 -39 9 51 -33 17 59
137 0 0 -37 46 17 17 50 9 57 49 -49 -38 2 21 -37 30 10 -40 33 30 -34 54 10
136 0 0 -39 10 15 17 49 46 56 49 -49 -39 25 46 -38 54 41 -41 51 57 -36 24 7
Uncertainty in time = +/- 25 secs
Prediction of 2011 Apr 16.0
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