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Updated: 2013 MAR 17, 21:41 UT
Event Rank : 67
(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 May 11 UT, the 74 km diameter asteroid (636) Erika will occult a 11.8 mag star in the constellation Sagittarius for observers along a north-to-south across Western Australia from near Broome to east of Esperance.
In the case of an occultation, the combined light of the asteroid and the star will drop by 2.2 mag to 13.9 mag (the magnitude of the asteroid) for at most 16.9 seconds.
This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Hugh Harris, 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
121 19 39 -13 0 0 20 14 24 69 208 -27 120 58 42 121 40 37 120 21 29 122 18 1
121 24 9 -14 0 0 20 14 49 69 210 -27 121 3 6 121 45 14 120 25 42 122 22 49
121 28 59 -15 0 0 20 15 14 70 212 -27 121 7 49 121 50 10 120 30 14 122 27 58
121 34 9 -16 0 0 20 15 39 71 214 -27 121 12 53 121 55 28 120 35 5 122 33 29
121 39 41 -17 0 0 20 16 5 72 216 -27 121 18 17 122 1 8 120 40 15 122 39 22
121 45 36 -18 0 0 20 16 30 72 218 -27 121 24 3 122 7 10 120 45 47 122 45 40
121 51 54 -19 0 0 20 16 55 73 220 -27 121 30 12 122 13 37 120 51 41 122 52 23
121 58 36 -20 0 0 20 17 21 73 223 -27 121 36 45 122 20 29 120 57 57 122 59 32
122 5 45 -21 0 0 20 17 47 74 226 -27 121 43 44 122 27 47 121 4 38 123 7 8
122 13 20 -22 0 0 20 18 13 75 229 -27 121 51 8 122 35 33 121 11 44 123 15 13
122 21 23 -23 0 0 20 18 39 75 232 -27 121 59 1 122 43 48 121 19 17 123 23 48
122 29 57 -24 0 0 20 19 5 75 236 -27 122 7 22 122 52 33 121 27 17 123 32 55
122 39 1 -25 0 0 20 19 31 76 239 -27 122 16 14 123 1 51 121 35 47 123 42 35
122 48 38 -26 0 0 20 19 57 76 243 -26 122 25 38 123 11 41 121 44 48 123 52 50
122 58 50 -27 0 0 20 20 23 76 247 -26 122 35 36 123 22 7 121 54 20 124 3 42
123 9 38 -28 0 0 20 20 49 76 251 -26 122 46 9 123 33 11 122 4 28 124 15 12
123 21 5 -29 0 0 20 21 16 76 255 -26 122 57 20 123 44 53 122 15 11 124 27 23
123 33 12 -30 0 0 20 21 42 76 259 -26 123 9 10 123 57 17 122 26 31 124 40 17
123 46 1 -31 0 0 20 22 9 76 264 -26 123 21 42 124 10 24 122 38 32 124 53 56
123 59 36 -32 0 0 20 22 35 76 267 -26 123 34 58 124 24 17 122 51 16 125 8 23
124 13 58 -33 0 0 20 23 2 76 271 -25 123 49 0 124 38 59 123 4 44 125 23 41
124 29 11 -34 0 0 20 23 28 75 275 -25 124 3 52 124 54 33 123 18 59 125 39 52
124 45 17 -35 0 0 20 23 55 75 278 -25 124 19 36 125 11 1 123 34 5 125 57 0
125 2 19 -36 0 0 20 24 21 74 281 -25 124 36 16 125 28 27 123 50 3 126 15 9
125 20 22 -37 0 0 20 24 48 74 284 -25 124 53 54 125 46 55 124 6 58 126 34 21
125 39 30 -38 0 0 20 25 15 73 287 -24 125 12 36 126 6 28 124 24 54 126 54 43
125 59 45 -39 0 0 20 25 41 72 290 -24 125 32 23 126 27 12 124 43 53 127 16 16
126 21 13 -40 0 0 20 26 8 72 292 -24 125 53 22 126 49 10 125 4 1 127 39 8
126 44 0 -41 0 0 20 26 34 71 294 -23 126 15 37 127 12 28 125 25 21 128 3 23
127 8 9 -42 0 0 20 27 1 70 296 -23 126 39 14 127 37 11 125 48 0 128 29 7
Uncertainty in time = +/- 15 secs
Prediction of 2013 Mar 17.0
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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