The second updates puts paths from both computors more close to each other.
Federspiel's update puts the path about 50km south of Manek's path.
For details see the individual reports.
Dear observers of minor planet occultations,
the about 40 km small minor planet (1036) Ganymed is currently displaying a very favourable perihelion opposition show which makes it an easy-to-observe object. At the moment it's V magnitude is about 10.7 mag. Ganymed is scheduled to occult the V=10.8 mag star ACT 63458 on the early morning (UT) of 1998 Aug 19 for observers in central Europe. The target star is located in northern Perseus, near the border to Cassiopeia (J2000 position 2h 2m 26.3s, +56° 35' 18"). The magnitude drop of this occultation will be around 0.7 mag, and the maximum duration is around 3 seconds (the asteroid is moving rather fast at 96.5"/h).
Ron Stone (USNO/Flagstaff) provided 17 positions of Ganymed which allowed me to compute a new orbit of this asteroid. Unfortunately, the latest measurement is of August 6 and not very close to the epoch of event. The orbit solution is numerically a bit unstable, but I believe it anyway. Strictly speaking, I computed two solutions: one from all positions (rms residuals 0.05" and 0.06" in RA and DE, respectively), and a second omitting the positions of Jul 2, Jul 18, Aug 1, Aug 5 which have residuals > 0.10" (rms residuals of the orbit solution of the remaining 13 positions then 0.03" and 0.04" in RA and DE, respectively).
Both solutions give paths about 0.5" north of Edwin Goffin's nominal prediction. Here is the path from the solution with all positions:
Central line for an occultation by (1036) Ganymed
(1036) Ganymed occults ACT 63458 (RA 2 2 26.3455 DE +56 35 17.92)
orbit from 17 USNO positions only, star ACT
Minimum geocentric distance:
date: 1998 8 19 time: 3 1 58.UT; d=2.05", PW=191.05 deg,pi=13.93",mu=96.55"/h
substellar point on earth (lat., long.), PA of least distance:
56.58 17.83 191.05
Lat. Long. hh:mm:ss UT StarAlt° StarAzi° SunAlt° SunAzi°
11.23 -65.17 2:53:36. ! 12.1 34.1 -57.0 316.3
16.86 -60.87 2:53:54. ! 19.1 35.1 -55.2 327.5
20.84 -57.54 2:54:11. ! 24.2 36.1 -53.2 335.2
24.06 -54.60 2:54:28. ! 28.5 37.1 -51.3 341.2
26.82 -51.86 2:54:46. ! 32.2 38.1 -49.3 346.3
29.24 -49.25 2:55: 3. ! 35.6 39.1 -47.4 350.7
31.41 -46.71 2:55:20. ! 38.7 40.2 -45.6 354.7
33.38 -44.20 2:55:38. ! 41.6 41.3 -43.7 358.3
35.17 -41.71 2:55:55. ! 44.3 42.4 -41.9 1.7
36.81 -39.22 2:56:12. ! 46.9 43.4 -40.2 5.0
38.31 -36.72 2:56:29. ! 49.4 44.5 -38.5 8.1
39.70 -34.20 2:56:47. ! 51.8 45.6 -36.8 11.0
40.96 -31.65 2:57: 4. ! 54.2 46.7 -35.1 14.0
42.13 -29.07 2:57:21. ! 56.4 47.8 -33.4 16.8
43.19 -26.46 2:57:39. ! 58.6 48.8 -31.8 19.6
44.15 -23.81 2:57:56. ! 60.7 49.7 -30.2 22.4
45.01 -21.13 2:58:13. ! 62.8 50.5 -28.6 25.1
45.79 -18.41 2:58:31. ! 64.8 51.2 -27.1 27.9
46.47 -15.66 2:58:48. ! 66.7 51.7 -25.5 30.6
47.06 -12.88 2:59: 5. ! 68.6 52.0 -24.0 33.3
47.56 -10.07 2:59:23. ! 70.5 51.9 -22.5 36.0
47.98 -7.24 2:59:40. ! 72.3 51.5 -21.0 38.6
48.31 -4.40 2:59:57. ! 74.0 50.4 -19.4 41.3
48.55 -1.54 3: 0:15. ! 75.6 48.7 -18.0 43.9
48.70 1.32 3: 0:32. ! 77.1 45.9 -16.5 46.5
48.78 4.17 3: 0:49. ! 78.5 41.9 -15.0 49.0
48.76 7.02 3: 1: 7. ! 79.7 36.3 -13.5 51.6
48.67 9.85 3: 1:24. ! 80.7 28.8 -12.1 54.0
48.49 12.65 3: 1:41. ! 81.3 19.5 -10.6 56.4
48.23 15.43 3: 1:58. ! 81.5 9.0 -9.1 58.8
47.90 18.17 3: 2:16. ! 81.3 358.5 -7.7 61.0
47.48 20.87 3: 2:33. ! 80.7 349.1 -6.2 63.2
46.99 23.53 3: 2:50. ! 79.8 341.4 -4.8 65.4
46.43 26.14 3: 3: 8. ! 78.6 335.5 -3.3 67.4
45.79 28.70 3: 3:25. ! 77.2 331.1 -1.8 69.4
45.08 31.21 3: 3:42. ! 75.6 328.0 -.4 71.2
This line crosses France (Bretagne, Paris, north of Strasbourg), southern Germany (Baden-Baden, Stuttgart, Landshut), Austria (Linz, Vienna), Slovakia (Bratislawa) before twilight becomes too strong.
If the orbit solution from the very best USNO positions only is used the path is shifted by about 90 km northward.
I recommend that observers within 100 km of the two paths (up to 200 km north and 100 km south of the decribed path) try their luck - they have a good chance of being sucessful.
All the best
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,
on August 19th around 3:02 UT is predicted occultation of 10.8 mag star GSC 3693.1699 with about 3.3 second duration. I have reduced 17 observation of minor planet obtained by Ron Stone (USNO/Flagstaff) with following results.
I have used 16 of his 17 observation, rejecting the August 1st position. Although the reduction showed the observations to be consistent and strictly numerically the path has uncertainity about 0.1" there was some signs this uncertainity may be larger.
The path I computed is shifted to north as compared with Edwin
Goffin's nominal path with about -20 seconds time shift. Current path runs from just south of
Great Britain at 3:00 UT, northern France, Belgium (3:01 UT), Germany, Czech Republic (3:02 UT)
and Slovakia where the twilight will probably significatly reduce the chances.
Due to the uncertainity upper mentioned and possible star position uncertainity observers up to 150 km north or south of this path should try to observe this event. Visually this will be quite hard to observe for only 0.7 mag deep brightness dip and the star being faint itself. On the other hand the star will be almost at zenith.
I wish you clear sky. Jan
Path computed with OCCULT 4.07 follows: Occultation of T3693.1699 by 1036 Ganymed on 1998 Aug 19 E. Longitude Latitude U.T. star sun - 19 00 00 + 47 25 57 2 58 29 65 -26 - 17 00 00 + 47 56 08 2 58 42 66 -25 - 15 00 00 + 48 23 18 2 58 54 68 -24 - 13 00 00 + 48 47 34 2 59 06 69 -23 - 11 00 00 + 49 09 02 2 59 18 70 -22 - 9 00 00 + 49 27 47 2 59 30 72 -21 - 7 00 00 + 49 43 55 2 59 42 73 -20 - 5 00 00 + 49 57 30 2 59 53 74 -19 - 3 00 00 + 50 08 34 3 00 05 75 -18 - 1 00 00 + 50 17 10 3 00 17 76 -17 + 1 00 00 + 50 23 22 3 00 29 77 -16 + 3 00 00 + 50 27 09 3 00 40 78 -15 + 5 00 00 + 50 28 33 3 00 52 79 -14 + 7 00 00 + 50 27 35 3 01 04 80 -13 + 9 00 00 + 50 24 14 3 01 16 81 -12 + 11 00 00 + 50 18 29 3 01 28 82 -11 + 13 00 00 + 50 10 19 3 01 40 82 -10 + 15 00 00 + 49 59 41 3 01 52 82 -9 + 17 00 00 + 49 46 33 3 02 04 82 -8 + 19 00 00 + 49 30 52 3 02 16 82 -7 + 21 00 00 + 49 12 34 3 02 29 81 -5
P.S. While writing this note I received Martin Federspiel results. His path is slightly to south of mine (about 100km) with comments explaining this feature.
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---
Dear observers of minor planet occultations,
a few minutes ago another high-quality position of (1036) Ganymed obtained by Ron Stone became available to me (observation date Aug 17). I recalculated the orbit, which became much more certain. The new path is about 25 km north of my path based on all 17 observations described earlier today. The remaining uncertainty of this path should be below 100 km in north-south direction.
Here are the numbers:
Central line for an occultation by (1036) Ganymed
(1036) Ganymed occults ACT 63458 (RA 2 2 26.346 DE +56 35 17.91)
orbit from 18 USNO positions only, star ACT
Minimum geocentric distance:
date: 1998 8 19 time: 3 2 10.UT; d=1.99", PW=191.29 deg,pi=13.93", mu=96.55"/h
substellar point on earth (lat., long.), PA of least distance:
56.58 17.78 191.29
Lat. Long. hh:mm:ss UT StarAlt° StarAzi° SunAlt° SunAzi°
11.37 -65.41 2:53:48. ! 12.1 34.1 -56.8 316.2
17.00 -61.12 2:54: 5. ! 19.1 35.1 -55.0 327.3
20.99 -57.79 2:54:22. ! 24.3 36.1 -53.0 335.0
24.22 -54.85 2:54:40. ! 28.5 37.1 -51.1 341.0
26.98 -52.11 2:54:57. ! 32.2 38.2 -49.1 346.0
29.41 -49.50 2:55:14. ! 35.6 39.2 -47.2 350.5
31.58 -46.96 2:55:32. ! 38.7 40.3 -45.4 354.4
33.55 -44.45 2:55:49. ! 41.6 41.4 -43.6 358.1
35.35 -41.96 2:56: 6. ! 44.4 42.5 -41.8 1.5
36.99 -39.46 2:56:24. ! 47.0 43.6 -40.0 4.7
38.50 -36.96 2:56:41. ! 49.5 44.7 -38.3 7.8
39.89 -34.44 2:56:58. ! 51.9 45.8 -36.6 10.8
41.16 -31.88 2:57:16. ! 54.2 46.9 -34.9 13.7
42.33 -29.30 2:57:33. ! 56.4 48.0 -33.3 16.6
43.39 -26.68 2:57:50. ! 58.6 49.0 -31.7 19.4
44.36 -24.03 2:58: 7. ! 60.7 50.0 -30.1 22.2
45.23 -21.34 2:58:25. ! 62.8 50.9 -28.5 24.9
46.00 -18.61 2:58:42. ! 64.8 51.6 -26.9 27.7
46.69 -15.85 2:58:59. ! 66.8 52.2 -25.4 30.4
47.29 -13.06 2:59:17. ! 68.7 52.5 -23.8 33.1
47.79 -10.24 2:59:34. ! 70.6 52.5 -22.3 35.8
48.21 -7.40 2:59:51. ! 72.3 52.1 -20.8 38.5
48.54 -4.54 3: 0: 9. ! 74.1 51.1 -19.3 41.1
48.79 -1.67 3: 0:26. ! 75.7 49.5 -17.8 43.8
48.94 1.21 3: 0:43. ! 77.3 46.8 -16.3 46.4
49.02 4.08 3: 1: 1. ! 78.7 42.8 -14.9 48.9
49.00 6.94 3: 1:18. ! 79.9 37.1 -13.4 51.5
48.91 9.78 3: 1:35. ! 80.9 29.6 -11.9 54.0
48.73 12.60 3: 1:53. ! 81.5 20.1 -10.5 56.4
48.48 15.39 3: 2:10. ! 81.8 9.2 -9.0 58.7
48.14 18.15 3: 2:27. ! 81.6 358.4 -7.5 61.0
47.73 20.86 3: 2:45. ! 80.9 348.7 -6.1 63.2
47.24 23.53 3: 3: 2. ! 80.0 340.8 -4.6 65.4
46.67 26.15 3: 3:19. ! 78.8 334.9 -3.2 67.4
46.03 28.72 3: 3:36. ! 77.3 330.5 -1.7 69.4
45.32 31.23 3: 3:54. ! 75.8 327.4 -.3 71.3
Good luck!
Martin
------------------------------------------------------------------------- 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,
yesterday Ron Stone (USNO/Flagstaff) sent me one more precise position (from August 17) close to the occultation date which permit recalculation (unfortunately not yearlier than today) of the earlier update.
From the total of 18 observations I have used 17 observations, still rejecting the August 1st position. Although the reduction showed the observations to be consistent and strictly numerically the path has uncertainity about 0.1" there was some signs this uncertainity may be larger.
This second update path I computed is shifted to north as compared with Edwin Goffin's nominal
path with only about -6 seconds time shift. This new update path is about 80km to the south of my first update
and runs about 50km to north of Martin's second update path.
Due to the uncertainity upper mentioned and possible star position uncertainity observers up to 150 km north or south of this path should try to observe this event. Visually this will be quite hard to observe for only 0.7 mag deep brightness dip and the star being faint itself. On the other hand the star will be almost at zenith.
I wish you clear sky. 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---