Update for (24) Themis - August 2/3, 1999
Update computed by Martin Federspiel; issued 28 Jul 1999 11:47:14 +0200 (CEST)
Update computed by Jan Manek; issued 27 Jul 1999 15:21:53 +0200 (CEST)
The updates differ only very slighly; using ACT star position instead of TRC1.0 in Manek's update would give
essential same updated path as is given by Federspiel.
Jan Manek's update
IOTA/IOTA-ES occultation update for
(24) Themis / TYC 6327 00551 1 event on 1999, August 2/3
visible from France, NW Spain, Cuba and Mexico
Summary
On the night August 2/3, 1999 will be occulted 10.7 mag star by a 127 km asteroid
(24) Themis. This update is based on USNO/Flagstaff astrometry for asteroid and TRC star position.
This update gives ~0.5 path width south shift and time ~1 minute earlier compared to
Goffin's nominal prediction.
Path uncertainity is ±2 path widths, because of scatter in declination and also
due to larger than usual star error position. However I think the true path will run
within ±1 path width of this updated one.
Path runs over Germany, but the star is extremely low there (and this is the same
for east-south Belgium). Acceptable altitude of star begins in France, around Paris
~2:32 UT. Path runs to WSW and shortly hits also very NW tip of Spain. After crossing
Atlantic ocean path runs over southern Bahama Islands ~2:39 UT, northern Cuba ~2:39.5 UT
and finally runs over northern Mexico at ~2:41.5 UT with Monterrey on the north limit.
The event at one glimpse:
* date and approx. UT time of event: August 3, 1999 @ 02:32 UT (Euro)
02:41 UT (Mexico)
* magnitude of target star: 10.7
* magnitude drop [mag]: 1.7
* estimated maximum duration [s]: 9.1
* path description: Path runs over Germany, but the star is extremely low
there (and this is the same for east-south Belgium).
Acceptable altitude of star begins in France, around Paris at ~2:32 UT.
Path then runs to WSW and shortly hits also very NW tip of Spain.
After crossing Atlantic ocean path runs over souther Bahama Islands
~2:39 UT, northern Cuba ~2:39.5 UT and finally runs over northern Mexico
at ~2:41.5 UT with Monterrey on the north limit.
The occultation path:
* approximate width [km]: 190
* uncertainty [path widths]: 2
* uncertainty in time [s]: 20
* map: attached
* remarks: Path uncertainities are given according to nominal star position
errors and expected asteroid positional accuracy.
!!!!!!!
Circles along the path are OCCULT exactly calculated centerline points.
!!!!!!!
Data for the target star:
* name: TYC 6327 00551 1
* constellation: Capricornus
* J2000 position [h,m,s; o,',"]: 20h 11m 20.403s; -21o 06' 29.97"
* position source: TRC1.0
* estimated accuracy ["]: 0.09" (0.07", 0.06")
* Johnson V mag [mag]: 10.69
* B-V [mag]: +1.01
* remarks: TYCHO quality flag is 5 (medium) with 'no investigation
for duplicity' flag set. ACT catalogue gives end figures 20.404s (+-0.06")
and 29.94" (+-0.08") for R.A. and Dec. respectively. I have decided to use
TRC position as it seems to be more reliable in this case.
Target star is in western Capricornus, 2.7 degrees SW of 5.4 mag star
sigma Cap (Neptune is 12' SE of this star). 14' SSW of target is 8.6 mag
star SAO 188990 and 8' NW of target is 9.5 mag star SAO 188991.
Just 1.3' NW of target is 11.8 mag star of about the same brightness
as the occulting asteroid.
Be sure to have enough time for finding the correct star in this poor area.
Data for the minor planet:
* general information:
number, name: (24) Themis
approx. diameter [km]: 127
* orbital information
orbit source: calculation Manek
source of used astrometry: USNO/Flagstaff (Ron Stone)
number of used observations: 40 USNO
number of rejected observations: 2 USNO
(1998 04 20.382858, 1999 06 12.451750)
time covered by the observations: 1998 02 26 - 1999 07 25
rms residuals ["] (RA,DE): 0.06", 0.10"
estimated positional accuracy at epoch of event ["]: 0.08"
remarks:
Data for the event:
* UT date and time of least geocentric approach: 02:36:56 UT
* approx. V mag of minor planet at event [mag]: 12.1
* geocentric parallax of minor planet ["]: 3.513
* magnitude drop [mag]: 1.7
* estimated maximum duration [s]: 9.1
* apparent motion of minor planet ["/h]: 27.68
* angular distance to moon, phase of moon [deg,%]: 77, 70%
* remarks:
Calculator(s): Jan Manek
Path coordinates:
Altitude
E. Longitude Latitude U.T. star sun
+ 8 00 00 + 51 06 42 2 31 45 4 -11
+ 6 00 00 + 50 09 53 2 31 47 5 -13
+ 4 00 00 + 49 12 22 2 31 49 7 -14
+ 2 00 00 + 48 14 16 2 31 51 8 -16
+ 0 00 00 + 47 15 42 2 31 54 10 -17
- 2 00 00 + 46 16 50 2 31 58 12 -19
- 4 00 00 + 45 17 48 2 32 02 13 -21
- 6 00 00 + 44 18 44 2 32 07 15 -22
- 8 00 00 + 43 19 46 2 32 12 17 -24
- 10 00 00 + 42 21 03 2 32 19 18 -25
- 12 00 00 + 41 22 43 2 32 25 20 -27
- 14 00 00 + 40 24 54 2 32 33 22 -28
- 16 00 00 + 39 27 43 2 32 40 23 -30
- 18 00 00 + 38 31 18 2 32 49 25 -31
- 20 00 00 + 37 35 47 2 32 58 26 -33
......... shortened .........................
- 72 00 00 + 22 55 47 2 38 39 40 -38
- 74 00 00 + 22 49 03 2 38 52 39 -37
- 76 00 00 + 22 44 31 2 39 06 39 -35
- 78 00 00 + 22 42 12 2 39 18 38 -34
- 80 00 00 + 22 42 05 2 39 31 36 -33
- 82 00 00 + 22 44 10 2 39 43 35 -31
- 84 00 00 + 22 48 29 2 39 55 34 -30
- 86 00 00 + 22 55 01 2 40 07 33 -28
- 88 00 00 + 23 03 46 2 40 18 31 -27
- 90 00 00 + 23 14 44 2 40 29 30 -25
- 92 00 00 + 23 27 56 2 40 39 29 -24
- 94 00 00 + 23 43 20 2 40 49 27 -22
- 96 00 00 + 24 00 56 2 40 58 26 -20
- 98 00 00 + 24 20 45 2 41 07 24 -19
-100 00 00 + 24 42 45 2 41 16 22 -17
-102 00 00 + 25 06 57 2 41 24 21 -15
-104 00 00 + 25 33 18 2 41 31 19 -13
-106 00 00 + 26 01 48 2 41 38 17 -12
-108 00 00 + 26 32 26 2 41 44 16 -10
-110 00 00 + 27 05 09 2 41 49 14 -8
-112 00 00 + 27 39 58 2 41 54 12 -6
-114 00 00 + 28 16 49 2 41 58 10 -4
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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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Martin Federspiel's update
IOTA/IOTA-ES occultation update for
(24) Themis/TYC 6327 00551 event on 1999 Aug 03
visible from Spain, Cuba, and Mexico
Summary
On the early morning (UT) of 1999 Aug 03 the 130 km large minor planet
(24) Themis will occult a 10.8 mag star in Capricornus for observers
in northwesternmost Spain, Cuba, and parts of Mexico.
The event takes place at low altitude for both observers in Spain
(near southwestern horizon) and Mexico (near southeastern horizon).
The path is about 0.7 path widths south of
Goffin's nominal prediction.
This update is based on a good orbit of the minor planet (from CAMC,
Bordeaux, and USNO positions) and the ACT position of the star (of medium
quality).
The event at one glimpse:
* date and approx. UT time of event: 1999 Aug 3 time: 2h 37m UT
* magnitude of target star: 10.8
* magnitude drop [mag]: 1.6
* estimated maximum duration [s]: 9
* rough path description: northwestern Spain (low altitude), Cuba, Mexico,
Baja California (low altitude)
The occultation path:
* approximate widths [km]: 130
* more detailed path description: northwesternmost Spain (low altitude),
Acklins Island, Cuba (south of Havana), Mexico (north of Tampico,
south of Monterrey, Torreon, Baja California (Punta Eugenia)
* uncertainty [path widths]: 1.2
* map: attached
* remarks: event 0.7 minutes earlier than and path about 0.7 path widths
south of E. Goffin's nominal prediction
Data for the target star:
* name: TYC 06327 00551
* constellation: Capricornus
* J2000 position [h,m,s; °,',"]: RA 20 11 20.404 DE -21 6 29.94
* position source: ACT
* estimated accuracy ["]: 0.05
* V mag [mag]: 10.8
* remarks: TYC quality flag 5 (medium astrometric quality, single star)
Data for the minor planet:
* general information:
mumber, name: (24) Themis
approx. diameter [km]: 130
* orbital information
orbit source: Federspiel
source of used astrometry: CAMC, Bordeaux, USNO
number of used observations: 197
number of rejected observations: several CAMC+Bordeaux, 4 USNO
time covered by the observations: 1985-1999
rms residuals ["] (RA,DE): 0.19",0.21"
estimated positional accuracy at epoch of event ["]: 0.1
remarks: good orbit
Data for the event:
* UT date and time of least geocentric approach:1999 Aug 03 @ 2h 37m 8s UT
* least geocentric distance ["]: 2.54
* uncertainty in time [s]: 13
* approx. V mag of minor planet at event [mag]: 12.1
* geocentric parallax of minor planet ["]: 3.51
* magnitude drop [mag]: 1.6
* estimated maximum duration [s]: 9
* apparent motion of minor planet ["/h]: 27.69"/h
* angular distance to moon, phase of moon [°,%]: 79°, 68%-
* remarks: event happens in low altitude for both observers in Spain
(southwestern horizon) and in Mexico (southeastern horizon)
Calculator(s): Martin Federspiel
Path coordinates:
Lat. Long. hh:mm:ss UT StarAlt° StarAzi° SunAlt° SunAzi°
52.42 12.51 2:31:54. ! .9 233.0 -8.1 46.5
45.46 -2.18 2:32: 9. ! 12.3 221.8 -19.6 34.8
42.53 -8.18 2:32:24. ! 17.3 217.3 -24.4 29.8
40.33 -12.74 2:32:39. ! 21.0 213.8 -27.9 25.9
38.51 -16.58 2:32:55. ! 24.1 210.8 -30.8 22.4
36.94 -19.98 2:33:10. ! 26.8 208.0 -33.2 19.1
35.56 -23.08 2:33:25. ! 29.1 205.4 -35.2 16.1
34.31 -25.96 2:33:40. ! 31.2 202.8 -37.0 13.0
33.17 -28.68 2:33:55. ! 33.0 200.3 -38.6 10.1
32.13 -31.26 2:34:11. ! 34.7 197.9 -39.9 7.1
31.17 -33.74 2:34:26. ! 36.2 195.4 -41.1 4.2
30.28 -36.14 2:34:41. ! 37.6 192.9 -42.1 1.2
29.46 -38.47 2:34:56. ! 38.8 190.4 -42.9 358.3
28.69 -40.74 2:35:12. ! 39.8 187.9 -43.5 355.4
27.98 -42.97 2:35:27. ! 40.8 185.3 -44.1 352.5
27.31 -45.17 2:35:42. ! 41.6 182.7 -44.4 349.6
26.69 -47.33 2:35:57. ! 42.2 180.1 -44.6 346.7
26.11 -49.48 2:36:13. ! 42.8 177.4 -44.7 343.8
25.58 -51.60 2:36:28. ! 43.2 174.8 -44.7 341.0
25.08 -53.72 2:36:43. ! 43.4 172.1 -44.5 338.3
24.62 -55.83 2:36:58. ! 43.6 169.4 -44.2 335.5
24.21 -57.94 2:37:13. ! 43.6 166.8 -43.7 332.9
23.82 -60.05 2:37:29. ! 43.5 164.1 -43.2 330.3
23.48 -62.17 2:37:44. ! 43.3 161.5 -42.5 327.8
23.18 -64.31 2:37:59. ! 42.9 158.9 -41.7 325.4
22.91 -66.46 2:38:14. ! 42.5 156.4 -40.8 323.1
22.68 -68.64 2:38:30. ! 41.8 153.9 -39.8 320.9
22.49 -70.85 2:38:45. ! 41.1 151.4 -38.7 318.7
22.35 -73.09 2:38:60. ! 40.2 149.0 -37.4 316.6
22.24 -75.38 2:39:15. ! 39.2 146.7 -36.0 314.6
22.19 -77.72 2:39:30. ! 38.1 144.4 -34.6 312.7
22.18 -80.13 2:39:46. ! 36.8 142.2 -32.9 310.9
22.23 -82.61 2:40: 1. ! 35.3 140.0 -31.2 309.1
22.34 -85.18 2:40:16. ! 33.7 137.9 -29.3 307.3
22.52 -87.86 2:40:31. ! 31.9 135.9 -27.3 305.6
22.78 -90.69 2:40:47. ! 30.0 133.8 -25.0 304.0
23.14 -93.69 2:41: 2. ! 27.7 131.8 -22.6 302.3
23.62 -96.94 2:41:17. ! 25.2 129.8 -19.8 300.6
24.26 -100.51 2:41:32. ! 22.3 127.7 -16.7 298.8
25.12 -104.59 2:41:47. ! 18.9 125.5 -13.1 296.9
26.38 -109.56 2:42: 3. ! 14.5 122.9 -8.6 294.6
28.61 -116.87 2:42:18. ! 7.9 119.3 -1.8 291.2
-------------------------------------------------------------------------
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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