Update for (69) Hesperia - February 22/23, 2000

Jan Manek's update

                  IOTA/IOTA-ES occultation update for
       (69) Hesperia / TYC 4930-00206-1 event on February 22/23, 2000
                     visible from Africa and Spain


Summary 

In the night of February 22/23, 2000 a 10.8 mag star TYC 4930-00206-1 will be occulted by a large 143 km asteroid (69) Hesperia. This update is based on USNO/Flagstaff and TMO astrometry for the asteroid and Tycho-2 star position.

The updated path shows ~1 path width north-east shift with no time correction compared to Edwin Goffin's nominal prediction.

The path of this occultation runs over Africa and then over Spain around 02:59 UT with Valencia in path. Within expected errors is also Barcelona and Madrid in Spain, very NE Portugal and very SW France with Pic du Midi.

Brighness drop is only ~0.8 magnitudes as the star and asteroid have the same magnitude. There is lack of good reference star close around the target star for visual observation so video record or CCD drift scan is recommended for truly reliable recording of the event.

The event at one glimpse:
 * date and approx. UT time of event: February 23, 2000 @ 02:59 UT
 * magnitude of target star: 10.8
 * magnitude drop [mag]: 0.8
 * estimated maximum duration [s]: 14.7
 * path description: given above
 * Goffin's original chart reference: A00_0209.

The occultation path:
 * approximate ground width [km]: 210
 * uncertainty [path widths]: 1.3
 * uncertainty in time [s]: 20
 * map: below
 * remarks: Path uncertainities are given according to nominal star
    position errors and expected asteroid positional accuracy.
    !!!!!!!
    Thick line indicates the centerline for this event.
    !!!!!!!

Data for the target star:
 * name: TYC 4930-00206-1
 * constellation: Leo
 * J2000 position [h,m,s; o,',"]: 11h 30m 53.172s; -01o 35' 08.38"
 * position source: Tycho-2
 * estimated accuracy ["]: 0.08" (0.05", 0.06")
 * V mag [mag]: 10.76
 * B-V [mag]: +0.60
 * remarks: 
     Target star is in very southern Leo, about 1.7 degrees SW of 4.3 mag 
     red star upsilon Leo = SAO 138298 or 1.4 degrees north of 4.8 mag star
     87 Leo = SAO 138238. There is also 7.3 mag star SAO 138252 only 20'
     to SE of target star. There is lack of good reference stars for this
     small brightness drop event.

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: (69) Hesperia
     approx. diameter [km]: 143
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone), TMO (Bill Owen)
     number of used observations: 69 USNO, 19 TMO
     number of rejected observations: 1 USNO, 1 TMO
     time covered by the observations: 1998 09 13 - 2000 02 04
     rms residuals ["] (RA,DE): 0.07", 0.07"
     estimated positional accuracy at epoch of event ["]: 0.07"
     remarks: 

Data for the event:
 * UT date and time of least geocentric approach: 02:57:29 UT
 * approx. V mag of minor planet at event [mag]: 10.8
 * geocentric parallax of minor planet ["]: 5.231
 * magnitude drop [mag]: 0.8
 * estimated maximum duration [s]: 14.7
 * apparent motion of minor planet ["/h]: 28.76
 * angular distance to moon, phase of moon [deg,%]: 23, 87%
 * remarks: 

Calculator(s): Jan Manek






Path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   ........ shortened ..........................
   + 10 00 00   + 31 14 47    2 56 44   44   -39
   +  8 00 00   + 32 47 23    2 57 09   44   -40
   +  6 00 00   + 34 22 23    2 57 35   44   -41
   +  4 00 00   + 35 59 38    2 58 00   44   -42
   +  2 00 00   + 37 38 54    2 58 26   44   -42
   +  0 00 00   + 39 19 56    2 58 51   43   -43
   -  2 00 00   + 41 02 28    2 59 16   43   -44
   -  4 00 00   + 42 46 12    2 59 41   42   -44
   -  6 00 00   + 44 30 49    3 00 05   41   -44
   -  8 00 00   + 46 15 56    3 00 28   40   -44
   - 10 00 00   + 48 01 10    3 00 51   39   -44
   - 12 00 00   + 49 46 05    3 01 12   38   -43
   - 14 00 00   + 51 30 17    3 01 33   36   -43
   - 16 00 00   + 53 13 16    3 01 53   35   -42
   - 18 00 00   + 54 54 37    3 02 11   33   -41
   - 20 00 00   + 56 33 52    3 02 29   32   -40
   ........ 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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