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Updated: 2013 AUG 13, 01:59 UT
Event Rank : 46
(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 Sep 29 UT, the 60 km diameter asteroid (101) Helena will occult a 12.5 mag star in the constellation Sagittarius for observers along a fairly narrow path across eastern Australia from Bowen across Queensland to eastern South Australia to Port Pirie, with Adelaide just inside the one sigma limit.
In the case of an occultation, the combined light of the asteroid and the star will drop by 0.6 mag to 12.1 mag (the magnitude of the asteroid) for at most 5.2 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 Limit1 Path Limit2 Error Limit1 Error Limit2
E. Longitude Latitude U.T. Alt Az Alt
o ' " o ' " h m s o o o o ' " o ' " o ' " o ' " o ' " o ' " o ' " o ' "
Longitude Latitude Longitude Latitude Longitude Latitude Longitude Latitude
134 15 8 -38 6 34 13 47 42 45 268 -47 133 48 29 -38 0 23 134 42 2 -38 12 38 132 35 11 -37 42 35 135 58 45 -38 29 2
134 59 34 -37 4 54 13 47 53 44 267 -48 134 33 4 -36 58 54 135 26 19 -37 10 47 133 20 9 -36 41 35 136 42 36 -37 26 40
135 44 40 -36 2 50 13 48 3 43 266 -49 135 18 17 -35 57 1 136 11 18 -36 8 32 134 5 43 -35 40 12 137 27 14 -36 23 52
136 30 33 -35 0 18 13 48 14 43 264 -50 136 4 16 -34 54 41 136 57 5 -35 5 49 134 51 58 -34 38 23 138 12 46 -35 20 37
137 17 18 -33 57 16 13 48 25 42 263 -51 136 51 5 -33 51 51 137 43 46 -34 2 35 135 38 59 -33 36 5 138 59 16 -34 16 49
138 5 2 -32 53 40 13 48 35 41 262 -53 137 38 52 -32 48 26 138 31 28 -32 58 46 136 26 52 -32 33 13 139 46 52 -33 12 24
138 53 52 -31 49 24 13 48 46 40 260 -54 138 27 42 -31 44 24 139 20 18 -31 54 18 137 15 45 -31 29 45 140 35 42 -32 7 19
139 43 57 -30 44 26 13 48 56 39 259 -55 139 17 45 -30 39 39 140 10 24 -30 49 6 138 5 45 -30 25 36 141 25 54 -31 1 28
140 35 24 -29 38 40 13 49 7 38 258 -57 140 9 8 -29 34 6 141 1 55 -29 43 5 138 57 0 -29 20 41 142 17 38 -29 54 46
141 28 24 -28 31 59 13 49 18 37 257 -58 141 2 3 -28 27 41 141 55 2 -28 36 10 139 49 39 -28 14 55 143 11 5 -28 47 6
142 23 10 -27 24 18 13 49 28 36 256 -59 141 56 40 -27 20 16 142 49 57 -27 28 12 140 43 54 -27 8 13 144 6 30 -27 38 21
143 19 55 -26 15 29 13 49 39 35 255 -60 142 53 13 -26 11 43 143 46 55 -26 19 5 141 39 57 -26 0 27 145 4 7 -26 28 21
144 18 56 -25 5 21 13 49 49 34 254 -62 143 51 58 -25 1 55 144 46 12 -25 8 38 142 38 2 -24 51 28 146 4 16 -25 16 57
145 20 31 -23 53 46 13 50 0 32 253 -63 144 53 14 -23 50 40 145 48 9 -23 56 42 143 38 27 -23 41 9 147 7 18 -24 3 56
146 25 6 -22 40 29 13 50 11 31 252 -65 145 57 23 -22 37 46 146 53 10 -22 43 0 144 41 32 -22 29 16 148 13 43 -22 49 3
147 33 10 -21 25 14 13 50 21 30 251 -66 147 4 55 -21 22 58 148 1 48 -21 27 19 145 47 43 -21 15 37 149 24 5 -21 31 58
148 45 20 -20 7 42 13 50 32 28 250 -67 148 16 25 -20 5 56 149 14 40 -20 9 14 146 57 32 -19 59 54 150 39 11 -20 12 17
150 2 26 -18 47 26 13 50 42 27 249 -69 149 32 40 -18 46 16 150 32 40 -18 48 20 148 11 38 -18 41 46 152 0 2 -18 49 27
151 25 33 -17 23 50 13 50 53 25 248 -70 150 54 41 -17 23 23 151 56 58 -17 23 59 149 30 55 -17 20 44 153 28 4 -17 22 43
152 56 15 -15 56 6 13 51 4 23 247 -71 152 23 55 -15 56 34 153 29 13 -15 55 17 150 56 34 -15 56 10 155 5 21 -15 50 59
Uncertainty in time = +/- 8 secs
Prediction of 2013 Aug 13.0
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