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Updated: 2017 May 19, 18:47 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 Jul 10 UT, the 75 km diameter asteroid (25) Phocaea will occult a 12.3 mag star in the constellation Vulpecula for observers along a path across western South Australia and north-western West Australia.
In the case of an occultation, the combined light of the asteroid and the star will drop by only 0.16 mag to 10.30 mag (the magnitude of the asteroid) for at most 13.3 seconds. This event will not be observable visually.
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.
Occultation of 2UCAC 41101818 by 25 Phocaea on 2017 Jul 10
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
142 40 35 -45 0 0 18 37 24 10 325 -36 143 15 46 142 5 34 143 35 32 141 46 2 0.02
141 41 25 -44 0 0 18 37 29 12 326 -37 142 15 44 141 7 15 142 35 1 140 48 10 0.03
140 44 30 -43 0 0 18 37 34 13 326 -37 141 18 1 140 11 7 141 36 51 139 52 29 0.03
139 49 40 -42 0 0 18 37 39 14 327 -38 140 22 27 139 17 1 140 40 51 138 58 46 0.03
138 56 44 -41 0 0 18 37 45 15 327 -39 139 28 49 138 24 45 139 46 50 138 6 54 0.03
138 5 32 -40 0 0 18 37 52 16 328 -40 138 36 59 137 34 12 138 54 39 137 16 41 0.03
137 15 58 -39 0 0 18 37 58 18 328 -40 137 46 49 136 45 13 138 4 8 136 28 2 0.04
136 27 53 -38 0 0 18 38 5 19 329 -41 136 58 10 135 57 41 137 15 10 135 40 48 0.04
135 41 10 -37 0 0 18 38 13 20 329 -41 136 10 56 135 11 29 136 27 38 134 54 54 0.04
134 55 44 -36 0 0 18 38 21 21 330 -42 135 25 0 134 26 32 135 41 25 134 10 13 0.04
134 11 28 -35 0 0 18 38 29 22 330 -43 134 40 17 133 42 44 134 56 26 133 26 41 0.04
133 28 19 -34 0 0 18 38 38 23 331 -43 133 56 41 133 0 0 134 12 36 132 44 11 0.04
132 46 10 -33 0 0 18 38 47 25 331 -44 133 14 7 132 18 16 133 29 48 132 2 40 0.04
132 4 57 -32 0 0 18 38 57 26 331 -44 132 32 32 131 37 26 132 48 0 131 22 3 0.04
131 24 38 -31 0 0 18 39 6 27 332 -45 131 51 51 130 57 28 132 7 6 130 42 17 0.04
130 45 7 -30 0 0 18 39 17 28 332 -45 131 11 59 130 18 18 131 27 4 130 3 18 0.04
130 6 22 -29 0 0 18 39 27 29 332 -46 130 32 55 129 39 52 130 47 48 129 25 2 0.04
129 28 19 -28 0 0 18 39 38 30 332 -46 129 54 34 129 2 7 130 9 17 128 47 27 0.04
128 50 56 -27 0 0 18 39 49 31 333 -47 129 16 54 128 25 1 129 31 27 128 10 30 0.04
128 14 9 -26 0 0 18 40 1 32 333 -47 128 39 51 127 48 30 128 54 15 127 34 9 0.04
127 37 57 -25 0 0 18 40 13 34 333 -48 128 3 23 127 12 32 128 17 39 126 58 19 0.04
127 2 16 -24 0 0 18 40 25 35 333 -48 127 27 28 126 37 6 127 41 36 126 23 0 0.04
126 27 4 -23 0 0 18 40 38 36 334 -48 126 52 3 126 2 7 127 6 3 125 48 10 0.04
125 52 20 -22 0 0 18 40 51 37 334 -49 126 17 7 125 27 36 126 30 59 125 13 45 0.04
125 18 1 -21 0 0 18 41 4 38 334 -49 125 42 36 124 53 28 125 56 22 124 39 44 0.04
124 44 6 -20 0 0 18 41 17 39 334 -49 125 8 29 124 19 44 125 22 9 124 6 6 0.04
124 10 32 -19 0 0 18 41 31 40 334 -50 124 34 45 123 46 20 124 48 19 123 32 48 0.04
123 37 18 -18 0 0 18 41 45 41 335 -50 124 1 22 123 13 16 124 14 50 122 59 49 0.04
123 4 23 -17 0 0 18 42 0 42 335 -50 123 28 17 122 40 29 123 41 41 122 27 7 0.04
122 31 44 -16 0 0 18 42 15 43 335 -50 122 55 30 122 7 59 123 8 49 121 54 41 0.04
121 59 20 -15 0 0 18 42 30 45 335 -50 122 22 59 121 35 43 122 36 13 121 22 30 0.04
121 27 11 -14 0 0 18 42 45 46 335 -50 121 50 42 121 3 41 122 3 53 120 50 31 0.04
120 55 14 -13 0 0 18 43 0 47 335 -51 121 18 39 120 31 50 121 31 46 120 18 44 0.04
120 23 28 -12 0 0 18 43 16 48 335 -51 120 46 47 120 0 10 120 59 51 119 47 8 0.04
119 51 53 -11 0 0 18 43 32 49 335 -51 120 15 6 119 28 40 120 28 6 119 15 40 0.04
Uncertainty in time = +/- 4 secs
Prediction of 2017 May 19.0
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