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Updated: 2017 DEC 27, 17:25 UT
Event Rank : 91
(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 2018 Feb 21 UT, the 71 km diameter asteroid (1241) Dysona will occult a 12.3 mag star in the constellation Scorpius for observers along a north-to-south path across Australia passing near Derby in WA, and into SA passing near Fowlers Bay.
In the case of an occultation, the combined light of the asteroid and the star will drop by 2.85 mag to 15.10 mag (the magnitude of the asteroid) for at most 2.8 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Hugh Harris, astrometry for the asteroid kindly provided by Bill Owen, astrometry for the asteroid kindly provided by the IAU Minor Planet Center.
This work has made use of data from the European Space Agency (ESA)mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, inparticular the institutions participating in the Gaia Multilateral Agreement.
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 Alt
E. Longitude Latitude U.T. Alt Az Alt Crn
o ' " o ' " h m s o o o o ' " o ' " o ' " o ' " o ' " o ' " o ' " o ' "
Longitude Latitude Longitude Latitude Longitude Latitude Longitude Latitude
121 5 23 -14 32 12 16 43 55 13 134 -64 121 53 22 -14 56 14 120 14 51 -14 5 23 122 30 13 -15 13 46 119 32 9 -13 41 28 0.61
123 18 6 -17 36 47 16 44 0 16 134 -60 123 59 39 -17 53 32 122 35 16 -17 18 36 124 32 3 -18 5 59 121 59 56 -17 2 52 0.67
125 3 8 -20 11 27 16 44 5 19 133 -57 125 41 23 -20 24 13 124 24 1 -19 57 43 126 11 26 -20 33 46 123 52 3 -19 45 57 0.70
126 32 3 -22 28 27 16 44 10 22 132 -54 127 8 21 -22 38 37 125 55 7 -22 17 33 127 36 58 -22 46 15 125 25 5 -22 8 15 0.71
127 50 12 -24 33 28 16 44 15 24 131 -52 128 25 14 -24 41 46 127 14 39 -24 24 33 128 52 55 -24 48 0 126 45 50 -24 16 58 0.72
129 0 31 -26 29 40 16 44 21 26 130 -50 129 34 43 -26 36 33 128 25 53 -26 22 16 130 1 47 -26 41 42 127 57 52 -26 15 57 0.72
130 4 52 -28 19 3 16 44 26 28 129 -48 130 38 31 -28 24 49 129 30 51 -28 12 51 131 5 10 -28 29 6 129 3 21 -28 7 32 0.72
131 4 29 -30 2 59 16 44 31 30 128 -46 131 37 47 -30 7 48 130 30 51 -29 57 45 132 4 11 -30 11 22 130 3 42 -29 53 15 0.72
132 0 15 -31 42 24 16 44 36 32 127 -44 132 33 21 -31 46 27 131 26 50 -31 38 0 132 59 37 -31 49 25 130 59 53 -31 34 11 0.73
132 52 50 -33 18 4 16 44 41 33 126 -42 133 25 51 -33 21 25 132 19 31 -33 14 21 133 52 4 -33 23 52 131 52 39 -33 11 7 0.73
133 42 43 -34 50 30 16 44 46 35 125 -40 134 15 46 -34 53 16 133 9 23 -34 47 24 134 42 1 -34 55 15 132 42 32 -34 44 40 0.73
134 30 18 -36 20 10 16 44 51 36 124 -39 135 3 28 -36 22 25 133 56 53 -36 17 36 135 29 49 -36 23 59 133 29 57 -36 15 19 0.73
135 15 56 -37 47 24 16 44 57 37 123 -37 135 49 17 -37 49 11 134 42 20 -37 45 19 136 15 46 -37 50 23 134 15 16 -37 43 26 0.73
135 59 50 -39 12 31 16 45 2 39 122 -36 136 33 26 -39 13 52 135 25 59 -39 10 52 137 0 8 -39 14 44 134 58 44 -39 9 20 0.73
Uncertainty in time = +/- 2 secs
Prediction of 2017 Dec 27.0
Use these links for further information:
[Planetary Occultations]
[Using the Predictions]
[Observing Details]
[Timing Details]
[Reporting Details]
[Report Form]
[Asteroid Occultation Results]
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