Update for (31) Euphrosyne - October 6/7, 2000

Jan Manek's update

IOTA/IOTA-ES occultation update for
         (31) Euphrosyne / TYC 2375-02899-1 on October 6/7, 2000
      visible from South Africa, Mozambique, Zimbabwe ... in Africa
                       and probably _not_ from Europe


Summary 

In the night of October 6/7, 2000 a 10.3 mag star TYC 2375-02899-1 will be occulted by a large 248 km asteroid (31) Euphrosyne. This update is based on USNO/Flagstaff and Hipparcos astrometry for the asteroid and Tycho-2 star position.

The updated path shows no significant path shift with time ~0.1 minutes earlier compared to Edwin Goffin's nominal prediction.

The path of this occultation runs over South Africa with Port Elisabeth and East London well in path ~22:10.3 UT, Bloemfontein just out of path at ~22:10.7 UT and Johannesburg/Pretoria just in path at ~22:10.9 UT. In fact almost all NE of South Africa is in path. Path then runs to north over Africa and finally just misses European continent with Gibraltar at closest point ~22:20.5 UT.

Very good event for South African observers, while European observers will almost surely have a miss, even at south Spain and Portugal, because the rather small expected errors leave only small probability for them.

Select some nearby reference star to help monitor this event with 1.2 mag drop.

The event at one glimpse:
 * date and approx. UT time of event: October 6, 2000 @ 22:11 UT (S.Af.)
                                                        22:20 UT (Euro)
 * magnitude of target star: 10.3
 * magnitude drop [mag]: 1.2
 * estimated maximum duration [s]: 20.3
 * path description: given above
 * Goffin's original chart reference: A00_1006

The occultation path:
 * approximate ground width [km]: 370
 * uncertainty [path widths]: 0.55
 * uncertainty in time [s]: 15
 * map: below
 * remarks: Path uncertainities are given according to nominal star
    position errors and expected asteroid positional accuracy.
    !!!!!!!
    Circles along path indicates the centerline for this event.
    They are more accurate than the path limit lines.
    !!!!!!!

Data for the target star:
 * name: TYC 2375-02899-1
 * constellation: Perseus
 * J2000 position [h,m,s; o,',"]: 04h 12m 11.234s; +33o 05' 44.52"
 * position source: Tycho-2
 * estimated accuracy ["]: 0.05" (0.03", 0.04")
 * V mag [mag]: 10.28
 * B-V [mag]: +0.51
 * remarks:
     Target star is in SE Perseus, about 4 degrees ENE of 2.9 mag star zeta
     Persei = SAO 56799. Target star is almost midway between 5.7 mag star
     SAO 57047 (33' to NNW) and 6.7 mag star SAO 57072 (35' to SSE of
     target). Select some nearby reference star to help monitor this event
     with 1.2 mag drop.

Close finding chart (prepared in GUIDE7):
 * occulted star is in center - labeled with cross
 * field is 3.0x3.0 degrees
 * limiting magnitude is 12.5
 * labeled stars have indicated SAO numbers





Data for the minor planet:
 * general information:
     number, name: (31) Euphrosyne
     approx. diameter [km]: 248
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone), Hipparcos
     number of used observations: 35 USNO, 16 HIP
     number of rejected observations: 4 USNO
     time covered by the observations: 1990 01 28 - 2000 09 25
     rms residuals ["] (RA,DE): 0.11", 0.12"
     estimated positional accuracy at epoch of event ["]: 0.07"
     remarks:

Data for the event:
 * UT date and time of least geocentric approach: 22:16.0 UT
 * approx. V mag of minor planet at event [mag]: 11.1
 * geocentric parallax of minor planet ["]: 4.777
 * magnitude drop [mag]: 1.2
 * estimated maximum duration [s]: 20.3
 * apparent motion of minor planet ["/h]: 33.03
 * angular distance to moon, phase of moon [deg,%]: 127, 63%
 * remarks:

Calculator(s): Jan Manek








Path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   ........ shortened ..........................
      o  '  "     o  '  "    h  m  s     o     o
     24 21  7   -36  0  0   22 10 14     7   -49
     25  7 13   -35  0  0   22 10 16     8   -50
     25 49 41   -34  0  0   22 10 18     9   -51
     26 28 49   -33  0  0   22 10 21    10   -52
     27  4 55   -32  0  0   22 10 23    11   -53
     27 38 11   -31  0  0   22 10 26    12   -53
     28  8 49   -30  0  0   22 10 30    13   -54
     28 37  1   -29  0  0   22 10 33    14   -55
     29  2 55   -28  0  0   22 10 37    15   -56
     29 26 40   -27  0  0   22 10 41    16   -57
     29 48 23   -26  0  0   22 10 45    17   -58
     30  8 10   -25  0  0   22 10 49    18   -59
     30 26  7   -24  0  0   22 10 53    19   -60
     30 42 20   -23  0  0   22 10 58    20   -61
     30 56 52   -22  0  0   22 11  3    21   -62
     31  9 48   -21  0  0   22 11  8    22   -63
     31 21 13   -20  0  0   22 11 13    23   -64
     31 31  8   -19  0  0   22 11 19    24   -65
     31 39 37   -18  0  0   22 11 24    25   -65
     31 46 42   -17  0  0   22 11 30    26   -66
     31 52 26   -16  0  0   22 11 36    26   -67
     31 56 51   -15  0  0   22 11 42    27   -68
     31 59 59   -14  0  0   22 11 48    28   -69
     32  1 51   -13  0  0   22 11 55    29   -70
   ........ shortened ..........................
      9 25 14    29  0  0   22 18 41    37   -64
      7 29 54    30  0  0   22 18 56    35   -62
      5 17 40    31  0  0   22 19 12    34   -60
      2 41 15    32  0  0   22 19 29    32   -58
   -  0 34 44    33  0  0   22 19 50    30   -55
   -  5 18 54    34  0  0   22 20 15    27   -52
   ........ shortened ..........................

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