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Updated: 2009 APR 02, 12:48 UT
Event Rank : 30
(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 18 UT, the 23 km diameter asteroid (1145) Robelmonte will occult a 11.9 mag star in the constellation Scorpius for observers along a narrow path across Western Australia.
In the case of an occultation, the combined light of the asteroid and the star will drop by 2.7 mag to 14.5 mag (the magnitude of the asteroid) for at most 5.5 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
118 54 53 -18 16 26 14 30 55 20 119 -66 119 10 55 -18 21 31 118 38 41 -18 11 13 120 19 32 -18 42 33 117 25 9 -17 46 45
119 24 38 -19 23 8 14 31 16 21 118 -67 119 40 13 -19 27 52 119 8 55 -19 18 17 120 47 3 -19 47 32 117 57 46 -18 55 35
119 51 9 -20 27 51 14 31 37 22 118 -67 120 6 21 -20 32 18 119 35 49 -20 23 19 121 11 43 -20 50 47 118 26 36 -20 2 5
120 14 49 -21 30 52 14 31 57 23 117 -67 120 29 42 -21 35 4 119 59 48 -21 26 35 121 33 52 -21 52 32 118 52 9 -21 6 36
120 35 55 -22 32 23 14 32 18 24 117 -67 120 50 34 -22 36 22 120 21 10 -22 28 19 121 53 43 -22 52 58 119 14 50 -22 9 24
120 54 43 -23 32 34 14 32 39 25 116 -67 121 9 9 -23 36 22 120 40 11 -23 28 42 122 11 30 -23 52 12 119 34 55 -23 10 43
121 11 25 -24 31 35 14 33 0 25 116 -66 121 25 41 -24 35 12 120 57 3 -24 27 52 122 27 20 -24 50 22 119 52 40 -24 10 42
121 26 9 -25 29 32 14 33 21 26 115 -66 121 40 16 -25 33 1 121 11 56 -25 25 58 122 41 23 -25 47 35 120 8 16 -25 9 30
121 39 3 -26 26 31 14 33 41 27 115 -66 121 53 4 -26 29 52 121 24 58 -26 23 6 122 53 45 -26 43 55 120 21 53 -26 7 14
121 50 15 -27 22 38 14 34 2 27 114 -65 122 4 10 -27 25 53 121 36 15 -27 19 20 123 4 30 -27 39 28 120 33 37 -27 4 1
121 59 48 -28 17 58 14 34 23 28 114 -65 122 13 40 -28 21 6 121 45 53 -28 14 45 123 13 45 -28 34 16 120 43 37 -27 59 56
122 7 48 -29 12 33 14 34 44 28 113 -65 122 21 37 -29 15 37 121 53 56 -29 9 27 123 21 32 -29 28 24 120 51 56 -28 55 3
122 14 18 -30 6 29 14 35 4 29 113 -64 122 28 5 -30 9 27 122 0 28 -30 3 27 123 27 54 -30 21 55 120 58 39 -29 49 26
122 19 21 -30 59 47 14 35 25 29 112 -64 122 33 7 -31 2 41 122 5 31 -30 56 49 123 32 54 -31 14 51 121 3 49 -30 43 8
122 22 59 -31 52 30 14 35 46 30 112 -63 122 36 45 -31 55 20 122 9 9 -31 49 36 123 36 34 -32 7 16 121 7 29 -31 36 13
122 25 14 -32 44 41 14 36 7 30 111 -62 122 39 1 -32 47 28 122 11 23 -32 41 50 123 38 54 -32 59 10 121 9 41 -32 28 42
122 26 6 -33 36 22 14 36 28 31 111 -62 122 39 55 -33 39 6 122 12 14 -33 33 34 123 39 57 -33 50 36 121 10 26 -33 20 39
122 25 38 -34 27 34 14 36 48 31 110 -61 122 39 29 -34 30 16 122 11 43 -34 24 49 123 39 43 -34 41 36 121 9 46 -34 12 6
122 23 49 -35 18 20 14 37 9 31 110 -61 122 37 43 -35 21 0 122 9 51 -35 15 37 123 38 11 -35 32 12 121 7 42 -35 3 3
122 20 39 -36 8 41 14 37 30 32 109 -60 122 34 36 -36 11 20 122 6 37 -36 6 0 123 35 23 -36 22 24 121 4 12 -35 53 34
122 16 7 -36 58 38 14 37 51 32 109 -59 122 30 10 -37 1 16 122 2 2 -36 55 58 123 31 17 -37 12 14 120 59 18 -36 43 39
Uncertainty in time = +/- 14 secs
Prediction of 2009 Apr 2.0
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