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Updated: 2013 JUL 04, 00:39 UT
Event Rank : 27
(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 2013 Aug 12 UT, the 18 km diameter asteroid (1182) Ilona will occult a 10.1 mag star in the constellation Scorpius for observers along a somewhat uncertain path across New Zealand passing near Darfield and Nelson.
In the case of an occultation, the combined light of the asteroid and the star will drop by 5.1 mag to 15.2 mag (the magnitude of the asteroid) for at most 3.5 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.
Centre Star Star Sun Path Limits Error Limits
E. Longitude Latitude U.T. Alt Az Alt Limit 1 Limit 2 Limit 3 Limit 4
o ' " o ' " h m s o o o o ' " o ' " o ' " o ' "
Longitude Longitude Longitude Longitude
173 26 54 -32 0 0 8 52 0 85 242 -37 173 32 39 173 21 9 174 1 3 172 52 45
173 20 42 -33 0 0 8 51 39 85 253 -37 173 26 31 173 14 53 173 55 14 172 46 10
173 14 20 -34 0 0 8 51 17 85 267 -37 173 20 13 173 8 27 173 49 16 172 39 24
173 7 46 -35 0 0 8 50 55 85 283 -37 173 13 43 173 1 49 173 43 8 172 32 25
173 0 59 -36 0 0 8 50 33 85 298 -36 173 7 1 172 54 58 173 36 47 172 25 11
172 53 59 -37 0 0 8 50 12 85 311 -36 173 0 5 172 47 52 173 30 15 172 17 43
172 46 43 -38 0 0 8 49 50 84 321 -36 172 52 54 172 40 32 173 23 28 172 9 57
172 39 11 -39 0 0 8 49 28 84 329 -35 172 45 28 172 32 55 173 16 28 172 1 54
172 31 22 -40 0 0 8 49 6 83 335 -35 172 37 44 172 25 0 173 9 11 171 53 32
172 23 14 -41 0 0 8 48 45 82 340 -35 172 29 42 172 16 46 173 1 37 171 44 50
172 14 45 -42 0 0 8 48 23 81 344 -34 172 21 19 172 8 11 172 53 45 171 35 45
172 5 55 -43 0 0 8 48 1 80 347 -34 172 12 35 171 59 15 172 45 33 171 26 16
171 56 41 -44 0 0 8 47 40 79 349 -34 172 3 28 171 49 54 172 36 59 171 16 22
171 47 2 -45 0 0 8 47 18 79 351 -33 171 53 56 171 40 8 172 28 2 171 6 0
171 36 55 -46 0 0 8 46 57 78 353 -33 171 43 57 171 29 53 172 18 40 170 55 9
171 26 19 -47 0 0 8 46 35 77 354 -32 171 33 29 171 19 9 172 8 51 170 43 45
171 15 11 -48 0 0 8 46 14 76 356 -32 171 22 29 171 7 53 171 58 33 170 31 47
171 3 29 -49 0 0 8 45 53 75 357 -32 171 10 56 170 56 1 171 47 44 170 19 11
170 51 9 -50 0 0 8 45 31 74 358 -31 170 58 45 170 43 32 171 36 20 170 5 55
170 38 9 -51 0 0 8 45 10 73 359 -31 170 45 55 170 30 22 171 24 19 169 51 55
Uncertainty in time = +/- 8 secs
Prediction of 2013 Jul 4.0
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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