Update for (511) Davida - August 11, 2000

Jan Manek's update

                    IOTA/IOTA-ES occultation update for
          (511) Davida / TYC 6877-00530-1 event on August 11, 2000
          visible from Russia, Moldavia, Romania, Bulgaria, Greece, 
                Albania, S Italy, Sicilia, Malta and Tunisia


Summary 

In the evening of August 11, 2000 a faint 10.6 mag star TYC 6877-00530-1 = PPM 734693 will be occulted by a large 337 km asteroid (511) Davida. This update is based on USNO/Flagstaff, TMO and Hipparcos astrometry for the asteroid and Tycho-2 star position.

The updated path shows small ~0.4 path width NW shift with time ~0.3 minutes earlier compared to Edwin Goffin's nominal prediction.

The path of this occultation runs over Russia at low altitudes with Moscow close to central line ~19:34.3 UT, Ukraine and Moldavia around 19:35 UT, Romania with Bucarest close to central line ~19:35.5 UT, Bulgaria ~19:35.5 UT, Greece and Albania ~19:36 UT, southern Italy, Sicilia and Malta around 19:37 UT. After crossing Meditterian Sea path runs over NW Africa staring at Tunisia ~19:38 UT.

As this even has only 1.6 mag drop, it is good there is close star slightly fainter that target, which can serve as reference star for better observation. Drift scan may be a possibility for someone, but keep in mind rather long duration ~30 seconds and expected time accuracy ~25 seconds, so ~90 seconds long drift should be possible. Target star is red which will help CCD observations. Almost full Moon only 2.5 degrees NE of target which will make the observation a hard one.

The event at one glimpse:
 * date and approx. UT time of event: August 11, 2000 @ 19:37 UT
 * magnitude of target star: 10.6
 * magnitude drop [mag]: 1.6
 * estimated maximum duration [s]: 30.9
 * path description: given above
 * Goffin's original chart reference: A00_0823

The occultation path:
 * approximate ground width [km]: 680
 * uncertainty [path widths]: 0.8
 * uncertainty in time [s]: 25
 * 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: PPM 734693 = TYC 6877-00530-1
 * constellation: Sagittarius
 * J2000 position [h,m,s; o,',"]: 18h 59m 41.385s; -24o 39' 07.21"
 * position source: Tycho-2
 * estimated accuracy ["]: 0.10 (0.06", 0.07")
 * V mag [mag]: 10.62
 * B-V [mag]: +1.12
 * remarks: 
     Target star is in middle Sagittarius, 1.9 degrees NE of 2.1 mag 
     star sigma Sagittarii = SAO 187448. There is 6.4 mag star SAO 187562 
     just 20' SSE of target star. Be careful - there is 11.1 mag star 
     GSC 6877.0693 only 54" WWS of target which can be used as nice 
     reference star for this event.

Close finding chart (prepared in GUIDE7):
 * occulted star is in center - labeled with cross
 * field is 2.0x2.0 degrees
 * limiting magnitude is 12.5
 * labeled stars have indicated SAO numbers





Data for the minor planet:
 * general information:
     number, name: (511) Davida
     approx. diameter [km]: 337
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone), TMO (Bill Owen),
                                Hipparcos
     number of used observations: 74 USNO, 5 TMO, 67 Hipparcos
     number of rejected observations: 3 USNO, 15 Hipparcos
     time covered by the observations: 1990 06 03 - 2000 07 26
     rms residuals ["] (RA,DE): 0.07", 0.06"
     estimated positional accuracy at epoch of event ["]: 0.07"
     remarks: 

Data for the event:
 * UT date and time of least geocentric approach: 19:38.8  UT
 * approx. V mag of minor planet at event [mag]: 11.9
 * geocentric parallax of minor planet ["]: 3.146
 * magnitude drop [mag]: 1.6
 * estimated maximum duration [s]: 30.9
 * apparent motion of minor planet ["/h]: 19.37
 * angular distance to moon, phase of moon [deg,%]: 3, 90%
 * remarks: 

Calculator(s): Jan Manek





Path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   ........ shortened ..........................
      o  '  "     o  '  "    h  m  s     o     o
     40  0  0    57 48 18   19 34  7     7   -14
     39  0  0    56 28 54   19 34 11     9   -15
     38  0  0    55 13 14   19 34 15    10   -16
     37  0  0    54  0 46   19 34 20    11   -16
     36  0  0    52 51 11   19 34 26    13   -17
     35  0  0    51 44 11   19 34 31    14   -18
     34  0  0    50 39 33   19 34 38    15   -18
     33  0  0    49 37  7   19 34 44    16   -19
     32  0  0    48 36 45   19 34 51    17   -19
     31  0  0    47 38 18   19 34 58    18   -19
     30  0  0    46 41 42   19 35  6    19   -20
     29  0  0    45 46 50   19 35 13    20   -20
     28  0  0    44 53 39   19 35 21    21   -20
     27  0  0    44  2  6   19 35 29    21   -21
     26  0  0    43 12  5   19 35 37    22   -21
     25  0  0    42 23 36   19 35 46    23   -21
     24  0  0    41 36 34   19 35 54    24   -21
     23  0  0    40 50 58   19 36  3    24   -21
     22  0  0    40  6 45   19 36 12    25   -21
     21  0  0    39 23 54   19 36 21    26   -21
     20  0  0    38 42 22   19 36 30    26   -21
     19  0  0    38  2  9   19 36 39    27   -20
     18  0  0    37 23 13   19 36 48    27   -20
     17  0  0    36 45 32   19 36 57    28   -20
     16  0  0    36  9  5   19 37  7    28   -20
     15  0  0    35 33 50   19 37 16    28   -20
     14  0  0    34 59 48   19 37 26    29   -19
     13  0  0    34 26 57   19 37 35    29   -19
     12  0  0    33 55 15   19 37 45    29   -19
     11  0  0    33 24 43   19 37 54    29   -18
     10  0  0    32 55 18   19 38  3    30   -18
      9  0  0    32 27  1   19 38 13    30   -17
      8  0  0    31 59 51   19 38 22    30   -17
      7  0  0    31 33 47   19 38 32    30   -16
   ........ 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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