Update for (738) Alagasta - June 8, 1999

Martin Federspiel's update

                     IOTA/IOTA-ES occultation update for 
                (738) Alagasta/Hip 74765 event on 1999 June 8
                          visible from north Africa


Summary 

On the evening of 1999 June 8 the 65 km large asteroid (738) Alagasta will occult the rather bright (7.3 mag) star HIP 74765 = SAO 159146 in Libra for observers along a narrow path in the near East and north Africa. The event will be easily visible due to the brightness of the target star and the magnitude drop of 7.3 mag. However, an uncertainty of 2.5 pathwidths remains for the path despite high quality data for both the star and the asteroid.

The updated path is shifted by 12 path widths south compared to Goffin's nominal prediction. The time shift is 2.5 minutes (this update being later than Goffin's prediction).

Path runs over south Portugal, Gibraltar and Morocco. Within expected errors is whole Portugal and NW + SW Spain. Madrid is probably too east, but observations from here may be valuable.

The event at one glimpse:
 * date and approx. UT time of event: 1999 June 8 from 21h 14m UT - 21h 30m UT
 * magnitude of target star: 7.3
 * magnitude drop [mag]: 7.3
 * estimated maximum duration [s]: 7.5
 * rough path description: Iran, Iraq, northern Saudi Arabia, southern Jordania,
   Sinai, northern Egypt, northern Libya, southern Tunesia, northern
   Algeria

The occultation path:
 * approximate widths [km]: 70
 * more detailed path description: Iran, Iraq, northern Saudi Arabia, 
   southern Jordania, Sinai, northern Egypt, northern Libya, southern 
   Tunesia, northern Algeria
 * uncertainty [path widths]: 2.5
 * map: see below
 * remarks: path shifted about 0.5" or 12 path widths southwards compared
   to E. Goffin's nominal prediction, time 2.5 minutes later than Goffin's
   nominal prediction

Data for the target star:
 * name: HIP 74765 = SAO 159 146
 * constellation: Libra
 * J2000 position [h,m,s; °,',"]: RA 15 16 48.605 DE -13  2 21.12
 * position source: Hipparcos
 * estimated accuracy ["]: 0.01
 * V mag [mag]: 7.3
 * remarks:

Data for the minor planet:
 * general information:
     mumber, name: (738) Alagasta
     approx. diameter [km]: 65
 * orbital information
     orbit source: computation Federspiel
     source of used astrometry: USNO, TMO
     number of used observations: 23 USNO, 2 TMO
     number of rejected observations: 1 USNO
     time covered by the observations: 1998 Feb - 1999 May 20
     rms residuals ["] (RA,DE): 0.07", 0.09"
     estimated positional accuracy at epoch of event ["]: 0.10
     remarks: significantly different orbit than Goffin's solution
     used in the nominal prediction

Data for the event:
 * UT date and time of least geocentric approach: 1999 June 8 @ 21 23 24.UT
 * least geocentric distance ["]: 3.03
 * uncertainty in time [s]: 17
 * approx. V mag of minor planet at event [mag]: 14.6
 * geocentric parallax of minor planet ["]: 4.40
 * magnitude drop [mag]: 7.3
 * estimated maximum duration [s]: 7.5
 * apparent motion of minor planet ["/h]: 21.59
 * angular distance to moon, phase of moon [°,%]: 139°, 32%-
 * remarks:

Calculator(s): Martin Federspiel





Path coordinates:

     Lat.     Long. hh:mm:ss UT  StarAlt° StarAzi°  SunAlt°  SunAzi°
     34.30    87.97 21:14:38. !      5.4    250.3    -17.6     44.8
     32.35    78.04 21:15: 2. !     13.6    244.7    -24.4     37.6
     31.38    72.15 21:15:27. !     18.4    241.2    -28.0     32.8
     30.72    67.46 21:15:51. !     22.2    238.3    -30.6     28.7
     30.23    63.41 21:16:15. !     25.3    235.7    -32.6     25.0
     29.85    59.77 21:16:40. !     28.0    233.2    -34.2     21.5
     29.56    56.42 21:17: 4. !     30.4    230.7    -35.4     18.1
     29.34    53.29 21:17:29. !     32.5    228.3    -36.3     14.8
     29.18    50.32 21:17:53. !     34.5    225.9    -37.1     11.6
     29.06    47.49 21:18:18. !     36.2    223.4    -37.6      8.5
     28.99    44.77 21:18:42. !     37.8    220.9    -38.0      5.5
     28.95    42.13 21:19: 7. !     39.3    218.3    -38.1      2.5
     28.95    39.57 21:19:31. !     40.6    215.7    -38.2    359.6
     28.98    37.06 21:19:55. !     41.7    213.0    -38.1    356.8
     29.04    34.61 21:20:20. !     42.7    210.2    -37.9    354.1
     29.12    32.20 21:20:44. !     43.6    207.4    -37.5    351.4
     29.23    29.83 21:21: 9. !     44.4    204.5    -37.1    348.8
     29.37    27.48 21:21:33. !     45.1    201.6    -36.5    346.3
     29.53    25.15 21:21:58. !     45.6    198.6    -35.9    343.9
     29.72    22.84 21:22:22. !     46.0    195.6    -35.1    341.5
     29.93    20.55 21:22:47. !     46.2    192.5    -34.3    339.2
     30.16    18.25 21:23:11. !     46.3    189.4    -33.4    337.0
     30.42    15.96 21:23:35. !     46.4    186.3    -32.4    334.9
     30.70    13.66 21:23:60. !     46.2    183.2    -31.3    332.8
     31.00    11.35 21:24:24. !     46.0    180.1    -30.1    330.7
     31.33     9.03 21:24:49. !     45.6    177.0    -28.9    328.8
     31.68     6.69 21:25:13. !     45.1    173.9    -27.6    326.8
     32.06     4.32 21:25:38. !     44.5    170.9    -26.2    324.9
     32.47     1.92 21:26: 2. !     43.7    167.9    -24.7    323.1
     32.91     -.51 21:26:26. !     42.8    164.9    -23.1    321.2
     33.38    -3.00 21:26:51. !     41.8    162.0    -21.5    319.4
     33.88    -5.55 21:27:15. !     40.7    159.1    -19.8    317.6
     34.41    -8.16 21:27:40. !     39.4    156.3    -18.0    315.8
     34.99   -10.86 21:28: 4. !     37.9    153.4    -16.0    314.0
     35.61   -13.66 21:28:29. !     36.4    150.6    -14.0    312.2
     36.28   -16.59 21:28:53. !     34.6    147.8    -11.8    310.3
     37.01   -19.66 21:29:18. !     32.7    145.0     -9.5    308.3
     37.80   -22.92 21:29:42. !     30.6    142.1     -7.1    306.3
     38.68   -26.43 21:30: 6. !     28.2    139.2     -4.4    304.1
     39.66   -30.27 21:30:31. !     25.5    136.0     -1.4    301.7
     40.78   -34.58 21:30:55. !     22.5    132.7      1.9    299.0
     42.11   -39.61 21:31:20. !     18.8    128.9      5.8    295.7
     43.80   -45.99 21:31:44. !     14.1    124.2     10.7    291.5
     46.52   -56.41 21:32: 9. !      6.5    116.6     18.5    284.1

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Martin Federspiel                 ******** E-mail: martin@astro.unibas.ch
Astronomisches Institut           ******** oder: federspi@astro.unibas.ch
der Universitaet Basel            **** oder: federspielm@ubaclu.unibas.ch  
Venusstr. 7                             Telefon: (CH)-61/2055413
CH-4102 Binningen (Schweiz)             Fax:     (CH)-61/2055455
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