Both updates agree well, the path is shifted west of Europen continent into Atlantic ocean.
For details see the individual reports.
Dear observers of minor planet occultations,
this is an update for the occultation of HIP 86271 (V=8.6 mag) by the V=15 mag asteroid (1428) Mombasa which is predicted to occur on the night 1998 Aug 13/14. According to Edwin Goffin's nominal prediction the about 60 km wide path should cross France, Spain, and western Africa. Tuboly Vince has distributed a similar prediction today which is probably not based on new data.
Ron Stone (USNO/Flagstaff) provided very accurate positions for the asteroid distributed over the past 90 days which allowed me to calculate a rather good orbit which is accurate enough for the epoch of occultation. Two out of 18 positions had to be rejected (Jun 20, Aug 7) for the orbit calculation.
The new occultation path from my orbit and the Hipparcos star position
is very disappointing for European observers: the path is shifted by
more than 1 arcsec westward and crosses the Atlantic Ocean; the only
continent it hits is Antarctica (see attached map).
Some Atlantic islands may have a chance of seeing the event - but there probably are no observers. After the Wotho event of July 17 this is the second promising occultation which is moved out of the European field of view within one month.
For the sake of completeness here are the numbers for the path:
Central line for an occultation by (1428) Mombasa
(1428) Mombasa occults HIP 86271 (RA 17 37 39.0977 DE -17 49 37.157)
orbit from 16 USNO observations only, star HIPPARCOS
Minimum geocentric distance:
date: 1998 8 13 time: 22 16 7.UT; d=.10", PW=275.72deg, pi=4.33",mu=17.21"/h
substellar point on earth (lat., long.), PA of least distance:
-17.82 -31.78 275.72
Lat. Long. hh:mm:ss UT StarAlt° StarAzi° SunAlt° SunAzi°
67.26 -20.81 22: 1: 6. ! 4.9 186.9 .0 310.5
56.48 -23.35 22: 1:36. ! 15.6 184.7 -6.0 307.9
50.51 -24.32 22: 2: 7. ! 21.6 184.0 -9.2 306.6
45.81 -24.99 22: 2:37. ! 26.3 183.6 -11.7 305.4
41.80 -25.52 22: 3: 7. ! 30.3 183.3 -13.7 304.3
38.21 -25.97 22: 3:37. ! 33.9 183.1 -15.5 303.3
34.93 -26.37 22: 4: 7. ! 37.2 182.9 -17.1 302.3
31.89 -26.74 22: 4:37. ! 40.3 182.7 -18.5 301.3
29.02 -27.08 22: 5: 8. ! 43.1 182.5 -19.8 300.3
26.30 -27.41 22: 5:38. ! 45.9 182.4 -21.0 299.3
23.70 -27.72 22: 6: 8. ! 48.5 182.2 -22.1 298.3
21.20 -28.02 22: 6:38. ! 51.0 182.1 -23.2 297.3
18.79 -28.31 22: 7: 8. ! 53.4 181.9 -24.1 296.3
16.45 -28.59 22: 7:38. ! 55.7 181.8 -25.0 295.2
14.17 -28.87 22: 8: 9. ! 58.0 181.6 -25.8 294.2
11.95 -29.14 22: 8:39. ! 60.2 181.5 -26.6 293.1
9.78 -29.41 22: 9: 9. ! 62.4 181.3 -27.3 292.0
7.65 -29.67 22: 9:39. ! 64.5 181.1 -27.9 290.9
5.55 -29.94 22:10: 9. ! 66.6 180.8 -28.5 289.8
3.49 -30.20 22:10:40. ! 68.7 180.6 -29.1 288.7
1.46 -30.46 22:11:10. ! 70.7 180.2 -29.6 287.6
-.55 -30.72 22:11:40. ! 72.7 179.8 -30.1 286.5
-2.53 -30.98 22:12:10. ! 74.7 179.3 -30.5 285.4
-4.50 -31.24 22:12:40. ! 76.7 178.6 -30.8 284.2
-6.45 -31.51 22:13:10. ! 78.6 177.8 -31.2 283.1
-8.39 -31.77 22:13:41. ! 80.5 176.5 -31.5 281.9
-10.31 -32.04 22:14:11. ! 82.5 174.6 -31.7 280.8
-12.23 -32.31 22:14:41. ! 84.3 171.4 -31.9 279.6
-14.14 -32.58 22:15:11. ! 86.2 165.0 -32.1 278.5
-16.05 -32.85 22:15:41. ! 87.9 147.7 -32.2 277.3
-17.95 -33.13 22:16:11. ! 88.7 84.3 -32.3 276.1
-19.86 -33.42 22:16:42. ! 87.5 35.0 -32.3 275.0
-21.77 -33.71 22:17:12. ! 85.8 21.9 -32.3 273.8
-23.68 -34.00 22:17:42. ! 83.9 16.6 -32.2 272.7
-25.60 -34.31 22:18:12. ! 82.0 13.9 -32.1 271.6
-27.52 -34.62 22:18:42. ! 80.1 12.2 -32.0 270.4
-29.46 -34.94 22:19:13. ! 78.2 11.1 -31.8 269.3
-31.41 -35.27 22:19:43. ! 76.2 10.4 -31.6 268.2
-33.38 -35.61 22:20:13. ! 74.2 9.9 -31.4 267.1
-35.36 -35.97 22:20:43. ! 72.3 9.5 -31.0 266.1
-37.37 -36.35 22:21:13. ! 70.2 9.3 -30.7 265.0
-39.40 -36.74 22:21:43. ! 68.2 9.1 -30.3 264.0
-41.46 -37.16 22:22:14. ! 66.1 9.1 -29.8 263.0
-43.56 -37.60 22:22:44. ! 64.0 9.1 -29.3 262.1
-45.69 -38.07 22:23:14. ! 61.9 9.1 -28.8 261.2
-47.86 -38.58 22:23:44. ! 59.7 9.3 -28.2 260.3
-50.08 -39.14 22:24:14. ! 57.5 9.5 -27.5 259.5
-52.35 -39.76 22:24:44. ! 55.2 9.7 -26.8 258.8
-54.69 -40.45 22:25:15. ! 52.8 10.1 -26.0 258.1
-57.10 -41.24 22:25:45. ! 50.4 10.5 -25.1 257.6
-59.59 -42.15 22:26:15. ! 47.9 11.1 -24.2 257.2
-62.18 -43.23 22:26:45. ! 45.2 11.9 -23.1 257.0
-64.89 -44.56 22:27:15. ! 42.5 12.9 -22.0 257.0
-67.73 -46.26 22:27:45. ! 39.6 14.3 -20.7 257.4
-70.74 -48.55 22:28:16. ! 36.5 16.3 -19.4 258.4
-73.94 -51.89 22:28:46. ! 33.1 19.3 -17.8 260.5
-77.38 -57.38 22:29:16. ! 29.4 24.5 -16.1 264.7
-81.03 -68.34 22:29:46. ! 25.3 35.1 -14.0 274.4
-84.35 -98.21 22:30:16. ! 20.4 64.6 -11.5 302.9
-83.50 -162.83 22:30:47. ! 13.9 128.8 -8.0 6.2
Sorry for the bad news - best regards anyway!
Martin Federspiel
------------------------------------------------------------------------- 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 -------------------------------------------------------------------------
Hi all,
I have finished reduction of Ron Stone's (USNO) observation received on Monday. I have used 16 from his 18 positions of minor planet (rejecting June 20 and August 7 positions) covering almost three months for independent computing a new orbit. This orbit is of high quality and resulting path shifts significantly west (to the unhabited Atlantic Ocean) of the Edwin Goffin's nominal one, passing originally over France and Spain.
This result confirms earlier finding of Martin Federspiel - the event becomes unobservable.
Best regards, Jan.
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-| --------------------------------------------------------------------U---U---