Update for (250) Bettina - October 2, 1998

  • Update computed by Martin Federspiel;   issued 25 Sep 1998 14:30:59 +0200 (CEST)

    • Martin Federspiel's update

                         IOTA/IOTA-ES occultation update for 
                    (250) Bettina/PPM 72742 event on 1998 Oct 2
                     visible from in central/northern Europe 

Summary
    A favourable occultation of a relatively bright star (V=7.9 mag) by the minor planet (250) Bettina occurs on the very early morning (UT) for observers in Europe. Unfortunately the undersigned has only limited astrometry for the asteroid which does only permit to calculate a medium quality orbit. Comparison with an alternative orbit provided by Bowell shows an offset of 0.46" between the two solutions. I consider my solution as the more probable one; the path goes over Spain, southern France, Germany, Poland. However, I estimate the possible error to be as large as 0.3" or 8 path widths. The path computed with the Bowell orbit is close to Goffin's nominal prediction. It crosses the UK and Norway and is probably too far north. I guess the true path will be somewhere between the two solutions presented here. Observers all over Europe are encouraged to monitor the event.
       

The event at one glimpse:
 * date and approx. UT time of event: 1998 Oct 2 time: 1h 40m UT
 * magnitude of target star: 7.9
 * magnitude drop [mag]: 5.1
 * estimated maximum duration [s]: 4
 * rough path description: accurate path uncertain; probably Spain, France
   Germany, Poland; may shift as far north as United Kingdom, Norway

The occultation path:
 * approximate widths [km]: 100
 * more detailed path description: does not make sense
 * uncertainty [path widths]: 8
 * map: attached
 * remarks: different orbits give paths 11 path widths apart; I consider
   the southern solution as more reliable

Data for the target star:
 * name: PPM 72742
 * constellation: northern Gemini
 * J2000 position [h,m,s; °,',"]: RA  7h 23m 18.366s DE +33° 41' 50.39"
 * position source: Hipparcos
 * estimated accuracy ["]: 0.01"
 * V mag [mag]: 7.91
 * remarks:

Data for the minor planet:
 * general information:
     mumber, name: (250) Bettina
     approx. diameter [km]: 86
 * orbital information
     orbit source: 2 orbits: Federspiel; Bowell 
     source of used astrometry: Federspiel: CAMC, USNO
     number of used observations: Federspiel: 26
     number of rejected observations: Federspiel: 3
     time covered by the observations: Federspiel: 1996 June-1997 December
     rms residuals ["] (RA,DE): Federspiel: 0.21,0.17
     estimated positional accuracy at epoch of event ["]: Federspiel: 0.3
     remarks: Bowell orbit computed from much longer arc; earlier astrometry
     not in ACT frame and of relatively low accuracy; I don't know how
     many recent and high quality observations were used for the orbit
     calculation

Data for the event:
 * UT date and time of least geocentric approach: 1998 Oct 2 @ 1h 42m 13s UT
 * least geocentric distance ["]: 1.76
 * uncertainty in time [s]: 26
 * approx. V mag of minor planet at event [mag]: 13.0
 * geocentric parallax of minor planet ["]: 3.22
 * magnitude drop [mag]: 5.1
 * estimated maximum duration [s]: 4
 * apparent motion of minor planet ["/h]: 41.58"/h
 * angular distance to moon, phase of moon [°,%]: 148, 84%+
 * remarks:

Calculator(s): Federspiel



    Updated path location for (250) Bettina on October 2, 1998

Path coordinates:
     solution with Federspiel orbit
      Lat.     Long. hh:mm:ss UT  StarAlt° StarAzi°  SunAlt°  SunAzi°
     28.04   -18.46  1:38:27. !     12.1     58.1    -64.0     20.3
     32.04   -13.11  1:38:36. !     18.1     61.0    -58.5     27.8
     35.10    -9.02  1:38:45. !     22.6     63.7    -54.1     32.3
     37.70    -5.50  1:38:55. !     26.3     66.4    -50.3     35.6
     40.01    -2.29  1:39: 4. !     29.5     69.0    -47.0     38.3
     42.12      .71  1:39:13. !     32.4     71.8    -43.9     40.8
     44.07     3.58  1:39:23. !     35.0     74.6    -41.0     43.0
     45.90     6.37  1:39:32. !     37.3     77.5    -38.3     45.1
     47.62     9.12  1:39:41. !     39.5     80.6    -35.7     47.2
     49.26    11.85  1:39:50. !     41.6     83.9    -33.3     49.3
     50.82    14.58  1:39:60. !     43.5     87.3    -30.9     51.4
     52.30    17.34  1:40: 9. !     45.2     90.9    -28.6     53.5
     53.72    20.14  1:40:18. !     46.9     94.7    -26.4     55.7
     55.08    23.00  1:40:28. !     48.4     98.8    -24.3     57.9
     56.38    25.92  1:40:37. !     49.8    103.1    -22.2     60.3
     57.62    28.94  1:40:46. !     51.0    107.6    -20.1     62.7
     58.81    32.05  1:40:55. !     52.2    112.4    -18.1     65.3
     59.93    35.28  1:41: 5. !     53.2    117.5    -16.1     68.0
     61.00    38.64  1:41:14. !     54.2    122.8    -14.2     70.8
     62.00    42.14  1:41:23. !     54.9    128.5    -12.3     73.8
     62.94    45.79  1:41:33. !     55.6    134.4    -10.4     77.0
     63.80    49.60  1:41:42. !     56.1    140.6     -8.5     80.4
     64.60    53.58  1:41:51. !     56.5    147.0     -6.7     83.9
     65.32    57.74  1:42: 0. !     56.8    153.7     -4.9     87.7
     65.95    62.07  1:42:10. !     56.9    160.6     -3.1     91.6
     66.49    66.57  1:42:19. !     56.9    167.7     -1.3     95.7


     solution with Bowell orbit:
     Lat.     Long. hh:mm:ss UT  StarAlt° StarAzi°  SunAlt°  SunAzi°
     33.79   -30.00  1:41:12. !      7.6     54.2    -59.6    355.9
     38.85   -23.66  1:41:21. !     14.6     58.2    -54.4      7.4
     42.34   -19.42  1:41:30. !     19.2     61.4    -50.4     13.5
     45.23   -15.90  1:41:40. !     22.8     64.4    -46.9     17.9
     47.79   -12.77  1:41:49. !     25.8     67.4    -43.7     21.4
     50.13    -9.86  1:41:58. !     28.5     70.4    -40.8     24.4
     52.30    -7.08  1:42: 8. !     30.8     73.4    -38.1     27.1
     54.34    -4.37  1:42:17. !     32.9     76.6    -35.5     29.7
     56.28    -1.69  1:42:26. !     34.8     79.9    -33.1     32.1
     58.14     1.00  1:42:35. !     36.6     83.3    -30.7     34.6
     59.92     3.72  1:42:45. !     38.1     87.0    -28.4     37.0
     61.64     6.52  1:42:54. !     39.5     90.8    -26.2     39.5
     63.30     9.43  1:43: 3. !     40.8     94.9    -24.1     42.1
     64.90    12.47  1:43:13. !     42.0     99.2    -22.0     44.8
     66.44    15.69  1:43:22. !     43.0    103.8    -20.0     47.7
     67.94    19.13  1:43:31. !     43.8    108.7    -18.0     50.8
     69.37    22.85  1:43:40. !     44.6    114.0    -16.0     54.2
     70.75    26.90  1:43:50. !     45.2    119.7    -14.1     58.0
     72.06    31.36  1:43:59. !     45.7    125.9    -12.2     62.1
     73.29    36.29  1:44: 8. !     46.1    132.6    -10.3     66.8
     74.44    41.79  1:44:18. !     46.3    139.9     -8.5     72.0
     75.47    47.95  1:44:27. !     46.4    147.9     -6.7     77.9
     76.37    54.83  1:44:36. !     46.4    156.6     -4.9     84.6
     77.12    62.47  1:44:45. !     46.3    166.0     -3.1     92.0
     77.68    70.85  1:44:55. !     46.0    176.2     -1.3    100.2

-------------------------------------------------------------------------
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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