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Updated: 2009 FEB 05, 22:51 UT
Event Rank : 22
(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 Feb 18 UT, the 29 km diameter asteroid (2450) Ioannisiani will occult a 11.5 mag star in the constellation Virgo for observers along a very narrow path across Western Australia from east of Esperence to Exmouth.
In the case of an occultation, the combined light of the asteroid and the star will drop by 4.4 mag to 15.9 mag (the magnitude of the asteroid) for at most 9.3 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Alice Monet, TMO astrometry for the asteroid kindly provided by Bill Owen, 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
124 40 0 -33 43 11 16 7 32 42 59 -45 124 27 47 -33 49 1 124 52 9 -33 37 20 123 10 34 -34 25 12 126 5 39 -33 1 18
123 57 56 -32 52 18 16 8 6 42 60 -46 123 45 48 -32 58 5 124 10 0 -32 46 31 122 29 9 -33 33 55 125 23 0 -32 10 49
123 15 23 -32 1 48 16 8 40 42 62 -47 123 3 20 -32 7 32 123 27 22 -31 56 4 121 47 10 -32 43 2 124 39 57 -31 20 41
122 32 20 -31 11 40 16 9 14 42 63 -47 122 20 20 -31 17 21 122 44 15 -31 5 59 121 4 37 -31 52 32 123 56 26 -30 30 55
121 48 44 -30 21 53 16 9 49 42 64 -48 121 36 49 -30 27 31 122 0 36 -30 16 15 120 21 29 -31 2 23 123 12 26 -29 41 28
121 4 36 -29 32 24 16 10 23 42 65 -49 120 52 43 -29 38 0 121 16 25 -29 26 49 119 37 44 -30 12 34 122 27 57 -28 52 19
120 19 54 -28 43 14 16 10 57 42 66 -50 120 8 3 -28 48 47 120 31 40 -28 37 42 118 53 20 -29 23 4 121 42 57 -28 3 28
119 34 35 -27 54 21 16 11 31 41 67 -51 119 22 47 -27 59 51 119 46 19 -27 48 51 118 8 17 -28 33 52 120 57 23 -27 14 54
118 48 38 -27 5 45 16 12 6 41 68 -52 118 36 51 -27 11 12 119 0 20 -27 0 17 117 22 33 -27 44 57 120 11 15 -26 26 34
118 2 1 -26 17 23 16 12 40 41 70 -52 117 50 16 -26 22 48 118 13 42 -26 11 58 116 36 5 -26 56 18 119 24 30 -25 38 30
117 14 43 -25 29 15 16 13 14 41 71 -53 117 2 58 -25 34 38 117 26 23 -25 23 53 115 48 51 -26 7 53 118 37 6 -24 50 38
116 26 40 -24 41 21 16 13 48 40 72 -54 116 14 55 -24 46 41 116 38 20 -24 36 0 115 0 50 -25 19 42 117 49 2 -24 3 0
115 37 50 -23 53 39 16 14 23 40 73 -55 115 26 6 -23 58 57 115 49 31 -23 48 20 114 11 58 -24 31 44 117 0 14 -23 15 33
114 48 12 -23 6 8 16 14 57 40 74 -55 114 36 26 -23 11 24 114 59 53 -23 0 52 113 22 12 -23 43 58 116 10 41 -22 28 17
113 57 41 -22 18 48 16 15 31 39 75 -56 113 45 54 -22 24 2 114 9 24 -22 13 34 112 31 31 -22 56 23 115 20 19 -21 41 11
113 6 15 -21 31 38 16 16 5 39 76 -57 112 54 26 -21 36 50 113 17 59 -21 26 26 111 39 49 -22 8 58 114 29 5 -20 54 15
112 13 49 -20 44 36 16 16 40 38 77 -57 112 1 58 -20 49 46 112 25 37 -20 39 26 110 47 5 -21 21 42 113 36 57 -20 7 27
111 20 22 -19 57 43 16 17 14 38 78 -58 111 8 27 -20 2 51 111 32 12 -19 52 34 109 53 12 -20 34 34 112 43 50 -19 20 47
110 25 47 -19 10 56 16 17 48 37 79 -58 110 13 48 -19 16 3 110 37 41 -19 5 50 108 58 7 -19 47 34 111 49 40 -18 34 13
109 30 0 -18 24 16 16 18 22 37 80 -59 109 17 57 -18 29 21 109 41 59 -18 19 11 108 1 44 -19 0 41 110 54 24 -17 47 46
Uncertainty in time = +/- 34 secs
[Prediction of 2009 Feb 6.0]
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[Observing Details]
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