Update for (257) Silesia - January 25/26, 2000

Jan Manek's update

                     IOTA/IOTA-ES occultation update for
          (257) Silesia / HIP 28748 event on January 25/26, 2000
       visible from SE Russia, NW Latvia, SE Estonia, middle Sweden
          and middle Norway in Europe and Alaska in North America


Summary 

In the night January 25/26, 2000 a 8.1 mag star HIP 28478 = SAO 77917 will be occulted by a 75 km asteroid (257) Silesia. This update is based on USNO/Flagstaff astrometry for the asteroid and HIPPARCOS star position.

The updated path shows large ~0.4" north shift with time ~2.4 minutes earlier compared to Edwin Goffin's nominal prediction.

The path of this occultation runs over SE Russia ~02:52 UT, NW Latvia and SE Estonia ~02:52.5 UT, grazes SE Finland ~02:53 UT, middle Sweden and Norway ~02:54 UT. Later path runs over Greenland, very north Canada and finally turn again to south and runs over Alaska, just north of Anchorage at ~03:08 UT.

The event at one glimpse:
 * date and approx. UT time of event: January 26, 2000 @ 02:53 UT (Euro)
                                                         03:08 UT (Alaska)
 * magnitude of target star: 8.1
 * magnitude drop [mag]: 5.8
 * estimated maximum duration [s]: 11.1
 * path description: given above
 * Goffin's original chart reference: A00_0118(.PS.GZ).

The occultation path:
 * approximate ground width [km]: 115
 * uncertainty [path widths]: 1.5
 * uncertainty in time [s]: 20
 * map: below
 * 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: HIP 28748 = SAO 77917 = PPM 95332 = GSC 1876.1361 = NSV 2811
 * constellation: Auriga
 * J2000 position [h,m,s; o,',"]: 06h 04m 16.232s; +28o 18' 03.38"
 * position source: HIPPARCOS
 * estimated accuracy ["]: 0.01" (0.01", 0.01")
 * V mag [mag]: 8.09
 * B-V [mag]: +1.24
 * remarks: 
     Target star is rather red (suspected variable NSV 2811) and it is in 
     southern Auriga, close to border with Gemini and Taurus. Target star 
     is 8.3 degrees east of 1.7 mag star beta Tauri or 2.7 degrees WSW of 
     4.3 mag star kappa Aurigae. There is 6.1 mag star SAO 77837 only 
     1 degree SW of target.

Close finding chart (prepared in GUIDE7):
 * occulted star is in center - labeled with cross
 * field is 2.0x2.0 degrees
 * limiting magnitude is 11.5
 * labeled stars have indicated SAO numbers





Data for the minor planet:
 * general information:
     number, name: (257) Silesia
     approx. diameter [km]: 73.5
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone)
     number of used observations: 42 USNO
     number of rejected observations: 8 USNO
     time covered by the observations: 1998 08 02 - 2000 01 13
     rms residuals ["] (RA,DE): 0.09", 0.07"
     estimated positional accuracy at epoch of event ["]: 0.07"
     remarks: 

Data for the event:
 * UT date and time of least geocentric approach: 03:02:05 UT
 * approx. V mag of minor planet at event [mag]: 13.9
 * geocentric parallax of minor planet ["]: 4.498
 * magnitude drop [mag]: 5.8
 * estimated maximum duration [s]: 11.1
 * apparent motion of minor planet ["/h]: 16.93
 * angular distance to moon, phase of moon [deg,%]: 97, 73%
 * remarks: 

Calculator(s): Jan Manek









Path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   ........ shortened ..........................
   + 38 00 00   + 50 47 49    2 51 40    8   -22
   + 36 00 00   + 52 02 08    2 51 46    9   -23
   + 34 00 00   + 53 15 13    2 51 54   11   -25
   + 32 00 00   + 54 26 52    2 52 03   13   -26
   + 30 00 00   + 55 36 57    2 52 12   14   -27
   + 28 00 00   + 56 45 18    2 52 22   16   -28
   + 26 00 00   + 57 51 46    2 52 33   17   -29
   + 24 00 00   + 58 56 15    2 52 45   19   -29
   + 22 00 00   + 59 58 38    2 52 57   20   -30
   + 20 00 00   + 60 58 51    2 53 09   21   -31
   + 18 00 00   + 61 56 51    2 53 22   22   -31
   + 16 00 00   + 62 52 34    2 53 34   24   -32
   + 14 00 00   + 63 46 00    2 53 47   25   -32
   + 12 00 00   + 64 37 07    2 54 00   26   -33
   + 10 00 00   + 65 25 57    2 54 13   27   -33
   +  8 00 00   + 66 12 30    2 54 26   27   -33
   +  6 00 00   + 66 56 49    2 54 38   28   -34
   +  4 00 00   + 67 38 56    2 54 51   29   -34
   +  2 00 00   + 68 18 54    2 55 03   30   -34
   ........ shortened ..........................
   -128 00 00   + 70 33 50    3 04 52   40   -19
   -130 00 00   + 70 01 40    3 05 06   40   -19
   -132 00 00   + 69 27 38    3 05 20   39   -18
   -134 00 00   + 68 51 41    3 05 35   39   -17
   -136 00 00   + 68 13 45    3 05 50   38   -16
   -138 00 00   + 67 33 46    3 06 05   38   -16
   -140 00 00   + 66 51 41    3 06 21   38   -15
   -142 00 00   + 66 07 28    3 06 37   37   -14
   -144 00 00   + 65 21 04    3 06 54   36   -13
   -146 00 00   + 64 32 27    3 07 11   36   -12
   -148 00 00   + 63 41 38    3 07 28   35   -11
   -150 00 00   + 62 48 35    3 07 46   34   -10
   -152 00 00   + 61 53 20    3 08 04   33    -8
   -154 00 00   + 60 55 55    3 08 22   32    -7
   -156 00 00   + 59 56 23    3 08 40   31    -6
   ........ shortened ..........................

----------------------------------------------------------------------------
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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