Update for (313) Chaldaea - April 10, 1999

Jan Manek's update

                      IOTA/IOTA-ES occultation update for
             (313) Chaldaea / HIP 33258 event on 1999, April 10/11
         visible from Labrador/Newfoundland, middle France and NW Italy


Summary 

On the night April 10/11, 1999 will be occulted 8.3 mag star by a 101km asteroid (313) Chaldaea. This update is based on USNO/Flagstaff nad TMO astrometry for asteroid and Hipparcos star position. European observers should locate the star well before the occultation itself, as the star will be low above horizont.

This update gives ~0.5 path width south shift and time about 0.4 minutes earlier compared to the Goffin's nominal prediction.

The event at one glimpse:
 * date and approx. UT time of event: April, 10, 1999 @ 23:36 UT (N.America)
                                                        23:38 UT (Euro)
 * magnitude of target star: 8.3
 * magnitude drop [mag]: 4.6
 * estimated maximum duration [s]: 4.2
 * path description: Path runs over Labrador/Newfoundland ~23:36 UT in twilight 
     zone. After crossing the Atlantic ocean shadow hits France ~23:37.7 UT at 
     Bretagne and runs over St-Nazaire, Nantes, Poitiers, Montlucon, Vichy, Lyon 
     and Chambery. Then it runs over Italy, but more to east it gets the star is 
     lower and lower; Torino is in path with star ~5 degrees above horizont at 
     ~23:38 UT. As the star is bright, it may be possible to observe at even those 
     quite low altitudes.

The occultation path:
 * approximate width [km]: 140
 * uncertainty [path widths]: 1
 * uncertainty in time [s]: 5
 * map: attached
 * remarks: Path uncertainities are given according to nominal star position 
    errors and expected asteroid positional accuracy. 
    !!!!!!!
    Circles along the path are OCCULT exactly calculated centerline points. 
    !!!!!!!

Data for the target star:
 * name: SAO 96272 = PPM 123256 = HIP 33258 = GSC 0760.2231
 * constellation: Gemini
 * J2000 position [h,m,s; o,',"]: 06h 55m 10.506s; +14o 13' 42.05"
 * position source: Hipparcos
 * estimated accuracy ["]: 0.01"  (0.01", 0.01")
 * Johnson V mag [mag]: 8.26
 * B-V [mag]: +1.41
 * remarks: Target star is quite red and is 4.7 degrees southeast of bright 2.0 mag 
     gamma Gem.  Try to locate the star well before occultation, it will be low 
     at the actual occultation time for Europe.

Data for the minor planet:
 * general information:
     mumber, name: (313) Chaldaea
     approx. diameter [km]: 101
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone), TMO (Bill Owen)
     number of used observations: 31 USNO, 28 TMO
     number of rejected observations: 2 USNO (1999 03 13.094653, 1998 10 23.491019)
     time covered by the observations: 1997 05 31 - 1999 03 13
     rms residuals ["] (RA,DE): 0.07", 0.07"
     estimated positional accuracy at epoch of event ["]: 0.10"
     remarks: Observations cover almost two years and are of excellent quality.

Data for the event:
 * UT date and time of least geocentric approach: 23:34:22 UT
 * approx. V mag of minor planet at event [mag]: 12.9
 * geocentric parallax of minor planet ["]: 4.883
 * magnitude drop [mag]: 4.6
 * estimated maximum duration [s]: 4.2
 * apparent motion of minor planet ["/h]: 65.89
 * angular distance to moon, phase of moon [deg,%]: 151, 32%
 * remarks: 

Calculator(s): Jan Manek





Path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   - 65 00 00   + 52 39 10   23 35 55   47    -5
   - 63 00 00   + 52 43 08   23 36 00   46    -6
   - 61 00 00   + 52 46 09   23 36 05   46    -7
   - 59 00 00   + 52 48 15   23 36 10   45    -8
   - 57 00 00   + 52 49 24   23 36 15   44    -9
   - 55 00 00   + 52 49 38   23 36 19   43   -10
   - 53 00 00   + 52 48 56   23 36 24   42   -11
   - 51 00 00   + 52 47 19   23 36 29   41   -12
   ........ ocean part cutted out ..............
   - 19 00 00   + 50 14 16   23 37 31   23   -28
   - 17 00 00   + 49 56 44   23 37 34   22   -29
   - 15 00 00   + 49 38 16   23 37 37   21   -30
   - 13 00 00   + 49 18 51   23 37 39   20   -30
   - 11 00 00   + 48 58 31   23 37 42   18   -31
   -  9 00 00   + 48 37 16   23 37 44   17   -32
   -  7 00 00   + 48 15 05   23 37 47   16   -33
   -  5 00 00   + 47 52 00   23 37 49   14   -33
   -  3 00 00   + 47 28 02   23 37 51   13   -34
   -  1 00 00   + 47 03 10   23 37 52   11   -35
   +  1 00 00   + 46 37 26   23 37 54   10   -35
   +  3 00 00   + 46 10 50   23 37 55    9   -36
   +  5 00 00   + 45 43 24   23 37 56    7   -36
   +  7 00 00   + 45 15 08   23 37 57    6   -37
   +  9 00 00   + 44 46 05   23 37 58    4   -37
   + 11 00 00   + 44 16 15   23 37 59    3   -38
   + 13 00 00   + 43 45 40   23 37 59    1   -38

----------------------------------------------------------------------------
Jan Manek
Stefanik Observatory                Private :
Petrin 205                          Werichova 950
118 46  Praha 1                     152 00  Praha 5 - Barrandov     |_|_|
Czech Republic                      Czech Republic                  /   \
Internet : jmanek@mbox.vol.cz                                      |-O-O-|
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