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Updated: 2017 AUG 01, 00:22 UT
Event Rank : 99
(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 2017 Sep 30 UT, the 75 km diameter asteroid (25) Phocaea will occult a 11.0 mag star in the constellation Delphinus for observers along a path just grazing the south-western Western Australia coast near Margaret River.
In the case of an occultation, the combined light of the asteroid and the star will drop by 0.59 mag to 10.60 mag (the magnitude of the asteroid) for at most 5.7 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, in particular 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 Limits Error Limits Alt
E. Longitude Latitude U.T. Alt Az Alt Limit 1 Limit 2 Limit 3 Limit 4 Crn
o ' " o ' " h m s o o o o ' " o ' " o ' " o ' "
Longitude Longitude Longitude Longitude
118 25 17 -43 0 0 11 6 0 33 18 -11 117 47 25 119 2 57 117 28 24 119 21 43 0.84
118 1 52 -42 0 0 11 5 53 34 19 -11 117 24 29 118 39 4 117 5 43 118 57 35 0.84
117 37 55 -41 0 0 11 5 47 35 19 -10 117 0 59 118 14 40 116 42 26 118 32 58 0.84
117 13 25 -40 0 0 11 5 40 35 20 -10 116 36 54 117 49 45 116 18 34 118 7 50 0.85
116 48 23 -39 0 0 11 5 33 36 21 -10 116 12 15 117 24 19 115 54 6 117 42 13 0.85
116 22 47 -38 0 0 11 5 26 37 22 -10 115 47 0 116 58 22 115 29 3 117 16 5 0.85
115 56 38 -37 0 0 11 5 19 38 22 -10 115 21 11 116 31 52 115 3 23 116 49 26 0.85
115 29 55 -36 0 0 11 5 11 39 23 -10 114 54 47 116 4 51 114 37 8 116 22 15 0.85
115 2 37 -35 0 0 11 5 4 39 24 -10 114 27 46 115 37 17 114 10 16 115 54 32 0.85
114 34 45 -34 0 0 11 4 56 40 25 -9 114 0 9 115 9 9 113 42 46 115 26 17 0.85
114 6 17 -33 0 0 11 4 48 41 26 -9 113 31 54 114 40 27 113 14 39 114 57 28 0.85
113 37 12 -32 0 0 11 4 40 42 27 -9 113 3 2 114 11 10 112 45 52 114 28 4 0.85
113 7 30 -31 0 0 11 4 32 42 28 -9 112 33 31 113 41 16 112 16 27 113 58 5 0.85
112 37 9 -30 0 0 11 4 24 43 29 -8 112 3 20 113 10 46 111 46 20 113 27 30 0.85
112 6 8 -29 0 0 11 4 15 44 30 -8 111 32 27 112 39 37 111 15 32 112 56 17 0.86
111 34 27 -28 0 0 11 4 7 44 31 -8 111 0 53 112 7 49 110 44 1 112 24 25 0.86
111 2 3 -27 0 0 11 3 58 45 33 -7 110 28 35 111 35 19 110 11 45 111 51 53 0.86
110 28 56 -26 0 0 11 3 49 45 34 -7 109 55 31 111 2 8 109 38 44 111 18 39 0.86
109 55 3 -25 0 0 11 3 40 46 35 -6 109 21 41 110 28 12 109 4 55 110 44 42 0.86
109 20 24 -24 0 0 11 3 31 46 37 -6 108 47 3 109 53 31 108 30 17 110 9 59 0.86
108 44 55 -23 0 0 11 3 21 47 38 -5 108 11 33 109 18 2 107 54 47 109 34 30 0.86
108 8 35 -22 0 0 11 3 12 47 39 -5 107 35 12 108 41 43 107 18 25 108 58 12 0.86
107 31 21 -21 0 0 11 3 2 47 41 -4 106 57 55 108 4 32 106 41 6 108 21 3 0.87
106 53 12 -20 0 0 11 2 52 48 42 -4 106 19 41 107 26 28 106 2 49 107 43 0 0.87
Uncertainty in time = +/- 2 secs
Prediction of 2017 Aug 1.0
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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