Update for (88) Thisbe - April 28, 2002 - South Africa

Jan Manek's update

                IOTA/IOTA-ES occultation update for
          (88) Thisbe / TYC 1343-01174-1 on April 28, 2002
                     visible from South Africa


Summary 

In the evening of April 28, 2002 a faint 11.5 mag star TYC 1343-01174-1 will be occulted by a 232 km asteroid (88) Thisbe. This update is based on USNO/Flagstaff and TMO astrometry for the asteroid and combined UCAC/Tycho-2 star position.

The updated path shows ~0.5 path width south shift with time 0.2 minutes earlier compared to Edwin Goffin's nominal prediction.

Updated path runs over South Africa around 15:58 UT with Johannesburg on north limit while Bloemfontein and Kimberley just out of south limit. Unfortunately it is rather faint star under strong evening twilight making star location very hard. Within uncertainties is somewhat larger area. Please check the path chart for details.

Clear sky and good luck !!!

The event at one glimpse:
 * date and approx. UT time of event: April 28, 2002 @ 16:58 UT
 * magnitude of target star: 11.5
 * magnitude drop [mag]: 1.9
 * estimated maximum duration [s]: 8.5
 * path description: given above
 * Goffin's original chart reference: A02_0420

The occultation path:
 * approximate ground width [km]: 320
 * uncertainty [path widths]: 0.7
 * uncertainty in time [s]: 6
 * map: below
 * remarks: Path uncertainties are given according to nominal star
    position errors and expected asteroid positional accuracy.

Data for the target star:
 * name: TYC 1343-01174-1
 * constellation: Gemini
 * J2000 position [h,m,s; o,',"]: 06h 52m 27.8828s; +21o 06' 43.309"
 * position source: UCAC star position combined with Tycho-2 proper motion
 * estimated accuracy ["]: 0.02" (0.012", 0.013")
 * V mag [mag]: 11.45
 * B-V [mag]: +0.78
 * remarks:
    Recent UCAC position was provided by Marion and Norbert Zacharias.
    Target star is in middle Gemini, about 2.8 degrees west of 4.0 mag star zeta Geminorum = SAO 79031.
    Purple stars in identification chart are so called 'non-star' objects in GSC; in dense fields
    the 'non-stars' are often real stars or blends of close pairs. Be careful.

Close finding chart (prepared in GUIDE7):
 * occulted star is in center - labeled with cross
 * field is 2.0x2.0 degrees
 * limiting magnitude is 13.0
 * labeled stars have indicated SAO numbers
 * remarks:





Data for the minor planet:
 * general information:
     number, name: (88) Thisbe
     approx. diameter [km]: 232
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone), TMO (Bill Owen)
     number of used observations: 131 USNO, 19 TMO
     number of rejected observations: 6 USNO, 2 TMO
     time covered by the observations: 1998 02 26 - 2002 03 27
     rms residuals ["] (RA,DE): 0.07", 0.06"
     estimated positional accuracy at epoch of event ["]: 0.04", 0.04"
     remarks:

Data for the event:
 * UT date and time of least geocentric approach: 15:56.5 UT
 * approx. V mag of minor planet at event [mag]: 13.2
 * geocentric parallax of minor planet ["]: 2.504
 * magnitude drop [mag]: 1.9
 * estimated maximum duration [s]: 8.5
 * apparent motion of minor planet ["/h]: 38.60
 * angular distance to moon, phase of moon [deg,%]: 137, 97%
 * remarks:

Calculator(s): Jan Manek





Path coordinates:
                                                   Latitude   Latitude
                  Center               Altitude       Path Limits
  E. Longitude   Latitude      U.T.   star   sun   Limit 1    Limit 2
   ........................... shortened .............................
      o  '  "     o  '  "    h  m  s     o     o    o  '  "    o  '  "
     27  0  0   -27 29  7   15 57 56    38    -4  -29  2  7  -25 58 34
     28  0  0   -27 47 17   15 57 60    37    -5  -29 20 32  -26 16 31
     29  0  0   -28  5 52   15 58  3    37    -6  -29 39 21  -26 34 53
     30  0  0   -28 24 51   15 58  6    36    -7  -29 58 34  -26 53 38
     31  0  0   -28 44 12   15 58  9    35    -8  -30 18 11  -27 12 46
     32  0  0   -29  3 57   15 58 12    35    -9  -30 38 11  -27 32 17
     33  0  0   -29 24  4   15 58 15    34   -10  -30 58 34  -27 52 10
     34  0  0   -29 44 33   15 58 18    33   -11  -31 19 18  -28 12 24
     35  0  0   -30  5 24   15 58 21    32   -11  -31 40 24  -28 33  0
     36  0  0   -30 26 35   15 58 24    32   -12  -32  1 51  -28 53 57
     37  0  0   -30 48  6   15 58 27    31   -13  -32 23 38  -29 15 14
     38  0  0   -31  9 57   15 58 29    30   -14  -32 45 44  -29 36 50
     39  0  0   -31 32  6   15 58 32    29   -15  -33  8 10  -29 58 45
     40  0  0   -31 54 34   15 58 34    28   -16  -33 30 54  -30 20 58
     41  0  0   -32 17 20   15 58 37    28   -17  -33 53 55  -30 43 29
     42  0  0   -32 40 23   15 58 39    27   -18  -34 17 14  -31  6 17
   ........................... shortened .............................

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