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Updated: 2012 Apr 18, 22:03 UT
Event Rank : 31
(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 2012 Apr 21 UT, the 21 km diameter asteroid (1817) Katanga will occult a 10.5 mag star in the constellation Ophiuchus for observers along a somewhat uncertain path across Queensland, passing near Proserpine, central New South Wales and central Victoria, passing near Melbourne.
In the case of an occultation, the combined light of the asteroid and the star will drop by 3.4 mag to 13.9 mag (the magnitude of the asteroid) for at most 7.4 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.
Occultation of TYC 0401-02149-1 by 1817 Katanga on 2012 Apr 21
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
149 12 22 -19 24 5 16 55 58 68 25 -48 149 18 26 -19 24 12 149 6 18 -19 23 58 149 44 23 -19 24 44 148 40 19 -19 23 27
148 50 49 -20 55 56 16 56 54 66 24 -48 148 56 56 -20 56 3 148 44 41 -20 55 48 149 23 9 -20 56 35 148 18 26 -20 55 17
148 28 37 -22 28 46 16 57 50 65 23 -48 148 34 48 -22 28 53 148 22 25 -22 28 38 149 1 18 -22 29 25 147 55 52 -22 28 6
148 5 43 -24 2 40 16 58 46 63 22 -47 148 11 59 -24 2 48 147 59 27 -24 2 33 148 38 48 -24 3 21 147 32 35 -24 2 0
147 42 3 -25 37 46 16 59 42 62 21 -47 147 48 24 -25 37 54 147 35 42 -25 37 39 148 15 34 -25 38 27 147 8 29 -25 37 6
147 17 32 -27 14 12 17 0 37 60 20 -47 147 23 59 -27 14 20 147 11 6 -27 14 4 147 51 32 -27 14 53 146 43 29 -27 13 30
146 52 5 -28 52 4 17 1 33 59 20 -47 146 58 38 -28 52 12 146 45 32 -28 51 56 147 26 37 -28 52 46 146 17 30 -28 51 22
146 25 34 -30 31 32 17 2 29 57 19 -47 146 32 14 -30 31 40 146 18 55 -30 31 24 147 0 41 -30 32 15 145 50 24 -30 30 50
145 57 52 -32 12 47 17 3 25 55 19 -46 146 4 39 -32 12 55 145 51 5 -32 12 39 146 33 38 -32 13 31 145 22 2 -32 12 3
145 28 49 -33 55 59 17 4 21 54 19 -46 145 35 44 -33 56 8 145 21 53 -33 55 51 146 5 18 -33 56 44 144 52 15 -33 55 15
144 58 12 -35 41 22 17 5 17 52 18 -46 145 5 16 -35 41 31 144 51 8 -35 41 14 145 35 30 -35 42 8 144 20 50 -35 40 37
144 25 48 -37 29 12 17 6 12 50 18 -45 144 33 2 -37 29 20 144 18 33 -37 29 3 145 4 0 -37 29 58 143 47 31 -37 28 25
143 51 17 -39 19 44 17 7 8 48 18 -45 143 58 43 -39 19 53 143 43 51 -39 19 35 144 30 31 -39 20 32 143 11 59 -39 18 56
143 14 18 -41 13 20 17 8 4 47 18 -44 143 21 57 -41 13 30 143 6 39 -41 13 11 143 54 40 -41 14 10 142 33 51 -41 12 31
142 34 21 -43 10 25 17 9 0 45 18 -44 142 42 15 -43 10 35 142 26 27 -43 10 16 143 16 2 -43 11 16 141 52 34 -43 9 35
Uncertainty in time = +/- 17 secs
Prediction of 2012 Apr 19.0
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[Using the Predictions]
[Observing Details]
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[Reporting Details]
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