RASNZ Occultation Section - Caia Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (952) CAIA - 2004 DEC 18

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 the time for your location)

On 2004 Dec 18 UT, the 82 km diameter asteroid (952) Caia will occult a 11.9 mag star in the constellation Aries for observers along a path across New Zealand.

In the case of an occultation, the combined light of the asteroid and the star will drop by 1.4 mag to 12.9 mag (the magnitude of the asteroid) for at most 15.6 seconds.

This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Ron Stone, 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 :

Event Rank : 98
(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).
Date and approx. UT time of event : 2004 Dec 18, 10:01 - 2004 Dec 18, 10:19 UT
(Refer to map(s) for your own location)
Magnitude of target star : 11.9
Magnitude drop [mag] : 1.4
Estimated maximum duration [s] : 15.6
Phase of moon, angular distance : 47 % sunlit, 64° distance
Sun : 147° distance
Rough path description : New Zealand

Data for the target star :

Name : 2UCAC 42532882
Constellation : Aries
J2000 position with proper motion to date of event [h,m,s ; °,',"]: RA: 03 18 59.1516 DE: +30 41 01.456
Position source : Pos: UCAC2, pm: UCAC2, pi:
Standard error : RA,DE ["]: ( .015, .016 )
V mag [mag] : 11.9
B mag [mag] : 0.0
Remarks : (none)

Data for the minor planet :

Number, name : (952) Caia
Approx. diameter [km] : 82
Approx. diameter [arcsec] : .073
Distance from Earth [AU] : 1.55900
Source of used astrometry : FASTT MPC (via Astdys)
Number of used observations : 479
Number of rejected observations : 42
Time covered by the observations : 1916 Oct 27 - 2004 Oct 09
1 sigma uncertainty ellipse (major, minor, PA) : 0.042, 0.020, 72°
Remarks : (none)
Orbital Elements for (952) Caia :
Update computed by : Steve Preston, Medina, Washington, USA. (OrbFit).

The Occultation Path :

Approximate projected width [km] : 178
Uncertainty interval [path widths] : +/- 0.36 (1 sigma)
Uncertainty interval [seconds] : +/- 8.4 (1 sigma)
Uncertainty interval approx RA,DE ["] : (+/- .044 +/- .028) (1 sigma)
Uncertainty ellipse (major, minor, PA) : ( .045", .026", 74° ) (1 sigma)
Approx speed of asteroid's shadow [km/s]: 5.2697
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.
Path Co-ordinates :

                  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
    152 52  5   -56  0  0   10 19 26     3    13     0  151 18 28  154 27 59  150 12 21  155 38 34
    153 27 17   -55  0  0   10 19 23     4    12    -1  151 55  4  155  1 45  150 49 57  156 11 17
    154  5  3   -54  0  0   10 19 20     5    12    -1  152 34  3  155 38 16  151 29 48  156 46 53
    154 45 19   -53  0  0   10 19 15     6    11    -2  153 15 23  156 17 28  152 11 54  157 25 20
    155 28  4   -52  0  0   10 19 10     7    11    -3  153 59  2  156 59 20  152 56 12  158  6 33

    156 13 19   -51  0  0   10 19  4     8    10    -5  154 45  1  157 43 51  153 42 43  158 50 34
    157  1  3   -50  0  0   10 18 56     9     9    -6  155 33 20  158 31  2  154 31 28  159 37 22
    157 51 19   -49  0  0   10 18 48    10     9    -7  156 24  2  159 20 55  155 22 29  160 27  0
    158 44 10   -48  0  0   10 18 38    11     8    -8  157 17  9  160 13 33  156 15 50  161 19 31
    159 39 40   -47  0  0   10 18 28    12     7    -9  158 12 45  161  9  1  157 11 32  162 14 59

    160 37 54   -46  0  0   10 18 16    13     6   -10  159 10 55  162  7 23  158  9 43  163 13 32
    161 39  0   -45  0  0   10 18  3    14     6   -11  160 11 46  163  8 49  159 10 26  164 15 17

                                                         Latitude   Latitude   Latitude   Latitude
    162  0  0   -44 40  1   10 17 58    15     5   -12  -43 19 33  -46  7 26  -42 25  5  -47 15 54
    163  0  0   -43 44 38   10 17 44    16     4   -13  -42 27  1  -45  8 26  -41 34 16  -46 13 35
    164  0  0   -42 51 37   10 17 30    17     4   -14  -41 36 33  -44 12 15  -40 45 20  -45 14 33
    165  0  0   -42  0 49   10 17 15    17     3   -15  -40 48  1  -43 18 38  -39 58 13  -44 18 27
    166  0  0   -41 12  5   10 17  0    18     2   -16  -40  1 21  -42 27 23  -39 12 49  -43 25  2

    167  0  0   -40 25 18   10 16 45    19     1   -17  -39 16 26  -41 38 21  -38 29  5  -42 34  3
    168  0  0   -39 40 22   10 16 29    20     0   -18  -38 33 13  -40 51 23  -37 46 56  -41 45 22
    169  0  0   -38 57 12   10 16 13    20   359   -19  -37 51 37  -40  6 22  -37  6 19  -40 58 48
    170  0  0   -38 15 43   10 15 57    21   359   -20  -37 11 34  -39 23 13  -36 27 11  -40 14 13
    171  0  0   -37 35 51   10 15 40    22   358   -21  -36 33  2  -38 41 49  -35 49 30  -39 31 33

    172  0  0   -36 57 33   10 15 23    22   357   -22  -35 55 57  -38  2  6  -35 13 12  -38 50 41
    173  0  0   -36 20 45   10 15  6    23   356   -23  -35 20 17  -37 24  1  -34 38 15  -38 11 32
    174  0  0   -35 45 25   10 14 48    24   355   -24  -34 45 59  -36 47 29  -34  4 39  -37 34  1
    175  0  0   -35 11 30   10 14 31    24   354   -25  -34 13  3  -36 12 28  -33 32 20  -36 58  6
    176  0  0   -34 38 58   10 14 13    24   353   -26  -33 41 24  -35 38 54  -33  1 16  -36 23 43

    177  0  0   -34  7 46   10 13 55    25   352   -26  -33 11  2  -35  6 45  -32 31 27  -35 50 49
    178  0  0   -33 37 52   10 13 38    25   351   -27  -32 41 56  -34 35 59  -32  2 51  -35 19 20
    179  0  0   -33  9 16   10 13 20    26   351   -28  -32 14  3  -34  6 34  -31 35 27  -34 49 16
    180  0  0   -32 41 54   10 13  2    26   350   -29  -31 47 22  -33 38 27  -31  9 13  -34 20 33

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