Updated: 2017 Sep 14, 22:02 UT
Event Rank : 100
(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 Oct 25 UT, the 280 km diameter asteroid (31) Euphrosyne will occult a 12.2 mag star in the constellation Auriga for observers along a very wide path across Northern Territory.
In the case of an occultation, the combined light of the asteroid and the star will drop by only 0.37 mag to 11.20 mag (the magnitude of the asteroid) for at most 17.5 seconds. This event will be very difficult to observe 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 UCAC4-689-044786 by 31 Euphrosyne on 2017 Oct 25 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 131 12 24 -15 41 33 16 14 32 12 32 -56 128 40 53 -17 19 17 133 22 20 -14 32 18 128 13 18 -17 39 14 133 41 50 -14 22 58 .... 133 28 19 -11 6 23 16 14 42 17 32 -59 131 29 21 -12 1 34 135 18 51 -10 22 47 131 9 19 -12 11 45 135 35 55 -10 16 41 -0.37 Uncertainty in time = +/- 2 secs Prediction of 2017 Sep 14.0
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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