This prediction update is supplied by Jan Manek of the Stefanik Observatory, Prague, and is based on USNO/Flagstaff astrometry for the minor planet and the ACT star position.

Summary:

This calculation gives a small 0.5 of a path width shift to the south and 0.3 minute later than the predictions prepared by Edwin Goffin. The path covers the northern tip of the North Island north of Whangarei at 13:43 UT, crosses the New South Wales coast between Coff's Harbour and Port Macquarie at 13:46.3 UT and the Western Australian coast on the northern outskirts of Perth at 13:51 UT (at low altitude - 18 degrees).

There is some confusion over the size of the asteroid. IRAS indicate a size of 108 km whereas another unidentified source quotes 66 km. This smaller size is used in the uncertainties quoted here so the above path limits may be conservative and include most of Perth with an occultation maximum duration as long as 10.6 seconds.

THE EVENT AT ONE GLIMPSE:

• Date and approx. UT time of event: 2000 February 5 @ 13:43 UT (NZ) and 13:49 UT (S Aus.)
• Magnitude of target star: 10.5
• Magnitude drop [mag]: 1.7
• Estimated maximum duration [s]: 6.5 (for 66km diameter)
• Goffin's original chart reference: A00_0204.PS.GZ

• Approximate width [km]: 105 (for 66 km diameter asteroid)
• Uncertainty [path widths]: 1.7
• Uncertainty in time [s]: 15
• Map: See below
• Remarks:Uncertainties are given on basis of nominal star position errors and expected asteroid positional accuracy.
• Circles along the path are OCCULT calculated exact centerline points.

• Name: TYC 1422 00422 1
• Constellation: Leo
• J2000 position [h,m,s; o,',"]: 10h 09m 46.926s; +18^o 15' 26.09"
• Position source: ACT
• Estimated accuracy ["]: 0.05" (0.03", 0.03")
• V mag [mag]: 10.49
• B-V [mag]: +0.82
• Remarks: TYCHO gives quality flag 4 (=high) with 'no investigation for duplicity' flag.
• Target star is in central western Leo, about 1.6 degrees NNE of 3.5 mag star eta Leonis or 2.9 degrees SW of the nice double star gamma Leonis (Algieba). There is a 6.9 mag star SAO 98969 about 19' NW of the target and closer is 8.0 mag star SAO 98978 only 6.5' SE of the target star.

• Number, name: (35) Leukothea
• Approx. diameter [km]: 66 (or 108 according to IRAS data)
• Orbit source: calculation Manek
• Source of used astrometry: USNO/Flagstaff (Ron Stone)
• Number of used observations:41 USNO
• Number of rejected observations: 3 USNO
• Time covered by the observations: 1998 09 14 - 2000 01 15
• Rms residuals ["] (RA,DE): 0.06", 0.06"
• Estimated positional accuracy at epoch of event ["]: 0.06"

• UT date and time of least geocentric approach: 2000 February 5 - 13:45:16 UTC
• Approx. V mag of minor planet at event [mag]: 12.0
• Geocentric parallax of minor planet ["]: 5.432
• Magnitude drop [mag]: 1.7
• Estimated maximum duration [s]: 6.5
• Apparent motion of minor planet ["/h]: 31.22
• Angular distance to moon, phase of moon [deg,%]: 166, 0%

Centerline path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   ........ shortened ..........................
   -177 00 00   - 38 10 06   13 41 58   33   -31
   -179 00 00   - 37 29 03   13 42 14   34   -32
   -181 00 00   - 36 49 25   13 42 30   35   -34
   -183 00 00   - 36 11 15   13 42 47   35   -35
   -185 00 00   - 35 34 38   13 43 04   36   -36
   -187 00 00   - 34 59 36   13 43 21   37   -37
   -189 00 00   - 34 26 12   13 43 39   37   -38
   -191 00 00   - 33 54 29   13 43 57   38   -39
   -193 00 00   - 33 24 27   13 44 15   38   -40
   -195 00 00   - 32 56 11   13 44 33   39   -41
   -197 00 00   - 32 29 42   13 44 52   39   -41
   -199 00 00   - 32 05 01   13 45 10   39   -42
   -201 00 00   - 31 42 10   13 45 28   39   -42
   -203 00 00   - 31 21 11   13 45 47   39   -43
   -205 00 00   - 31 02 05   13 46 05   39   -43
   -207 00 00   - 30 44 53   13 46 23   38   -43
   -209 00 00   - 30 29 37   13 46 41   38   -43
   -211 00 00   - 30 16 17   13 46 59   37   -43
   -213 00 00   - 30 04 54   13 47 16   37   -43
   -215 00 00   - 29 55 29   13 47 34   36   -43
   -217 00 00   - 29 48 03   13 47 51   35   -42
   -219 00 00   - 29 42 36   13 48 07   34   -42
   -221 00 00   - 29 39 10   13 48 24   33   -41
   -223 00 00   - 29 37 44   13 48 40   32   -41
   -225 00 00   - 29 38 18   13 48 55   31   -40
   -227 00 00   - 29 40 54   13 49 10   30   -39
   -229 00 00   - 29 45 32   13 49 25   29   -38
   -231 00 00   - 29 52 11   13 49 39   28   -37
   -233 00 00   - 30 00 51   13 49 52   27   -36
   -235 00 00   - 30 11 33   13 50 05   25   -35
   -237 00 00   - 30 24 17   13 50 17   24   -34
   -239 00 00   - 30 39 02   13 50 29   22   -33
   -241 00 00   - 30 55 48   13 50 40   21   -31
   -243 00 00   - 31 14 34   13 50 50   19   -30
   -245 00 00   - 31 35 19   13 50 59   18   -28
   -247 00 00   - 31 58 04   13 51 08   16   -27
   -249 00 00   - 32 22 47   13 51 16   15   -26
   -251 00 00   - 32 49 26   13 51 23   13   -24
   ........ shortened ..........................

Calculator: Jan Manek

Set out below is a more detailed finder chart for the target star. The occulted star is in the centre marked with a cross. The field size is 2.0 X 2.0 degrees and has a limiting magnitude of 12.5. Labelled stars have SAO identifiers marked. Chart prepared by Jan Manek.

IMPORTANT NOTE!

Astrometric updates such as these should not be taken as definitive, but rather only as an indication of where the true track may lie relative to the original predicted track. Observers must bear in mind that later astrometry, in which the target star is measured in the same field as the asteroid, may still reveal substantial changes to the predicted track and time of the event. For this reason it is most important that observers far from the predicted track still monitor the event.