Update for (102) Miriam event on August 2nd, 1998

Jan Manek's path compared to Martin Federspiel's is about 1 path width North and 15 seconds earlier. The agreement is quite good.
For details check both individual texts.

The 11.0 magnitude star TAC -07° 10906 = TYC 5757 00009 is predicted to be occulted by minor planet (102) Miriam on the night 2/3 August 1998.

Based on 11 positions obtained by Ron Stone (U.S.N.O.) covering 32 days (June 16 - July 18) and ACT star position I have computed an update for this event. I had to compute a new orbit instead of using differential corrections and although the RMS errors are less than 0.05", due to short time interval and last observation being 2 weeks before occultation, there can be even larger error in the prediction (the star position has an uncertainity about 0.1" too).

Compared to Edwin Goffin's nominal prediction available at http://sorry.vse.cz/~ludek/mp/1998/0802mir.gif the path shifts slightly to north with +1.5 minute time correction, the large corrections for asteroid positions being almost completely canceled using ACT instead of TYCHO star position.

This updated path now runs over southern Sweden around 23:51:30 UT, Denmark at 23:52 UT and central Great Britain around 23:54 UT. Due to the uncertainity also observers from NW Poland, N Germany, S Norway, Netherland, Belgium, N and NW France and Ireland have some chance to see this event. Path coordinates computed with OCCULT 4.07 are listed below.

I would like to emphasize the star has only 11.0 magnitudes visually and drop will be only 1.0 magnitude with 12.3 seconds durations, so this event will require larger telescopes (8 inches or larger) and it is on the limit of being observed visually.

All reasonable observations sent to me will be posted on the Asteroidal occultation observations (EURO) page.

I wish you success, Jan.

Occultation of TYC 5757 00009 by  102 Miriam on 1998 Aug 2
  E. Longitude    Latitude     U.T.    star  sun
   - 20 00 00   + 47 49 29   23 57 03   31   -22
   - 18 00 00   + 48 23 01   23 56 41   31   -22
   - 16 00 00   + 48 57 33   23 56 19   31   -22
   - 14 00 00   + 49 33 01   23 55 57   31   -21
   - 12 00 00   + 50 09 21   23 55 36   31   -21
   - 10 00 00   + 50 46 29   23 55 14   31   -21
   -  8 00 00   + 51 24 22   23 54 53   30   -20
   -  6 00 00   + 52 02 55   23 54 32   30   -20
   -  4 00 00   + 52 42 03   23 54 12   30   -20
   -  2 00 00   + 53 21 43   23 53 52   29   -19
   +  0 00 00   + 54 01 49   23 53 33   29   -18
   +  2 00 00   + 54 42 17   23 53 14   28   -18
   +  4 00 00   + 55 23 01   23 52 56   27   -17
   +  6 00 00   + 56 03 58   23 52 38   26   -16
   +  8 00 00   + 56 45 02   23 52 21   26   -16
   + 10 00 00   + 57 26 07   23 52 05   25   -15
   + 12 00 00   + 58 07 09   23 51 49   24   -14
   + 14 00 00   + 58 48 03   23 51 34   23   -13
   + 16 00 00   + 59 28 44   23 51 20   22   -12
   + 18 00 00   + 60 09 07   23 51 07   22   -12
   + 20 00 00   + 60 49 06   23 50 54   21   -11
   + 22 00 00   + 61 28 38   23 50 42   20   -10
   + 24 00 00   + 62 07 38   23 50 30   19    -9
   + 26 00 00   + 62 46 02   23 50 20   18    -8
   + 28 00 00   + 63 23 46   23 50 10   17    -7
   + 30 00 00   + 64 00 46   23 50 01   16    -6

I don't expect I will calculate any new update because I'm leaving tomorrow for vacation (August 1 - 9).

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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Dear observers of minor planet occultations,

Ron Stone (USNO/Flagstaff) provided astrometric observations of (102) Miriam which allow an updated prediction for the path of the occultation of TYC 5757 0009 (V=11.1 mag) during the night of 1998 Aug 2/3.

There is a clear offset of the USNO Miriam positions with respect to the MPC 25186 orbit of O-C(right ascension)=+0.68" and O-C(declination)=-0.31". Surprisingly this - in combination with the ACT position of the star - does not translate into a a significant shift of the path compared to Edwin Giffin's nominal prediction; but there is a time shift of +2 minutes compared to Edwin's calculation. (I applied the differential correction with negative sign to the ACT position of the star.)

The updated path goes as follows (southernmost Sweden, southern Denmark, northernmost Germany, coast of the Netherlands, Channel between UK and France, north of Bretagne in France; see attached map):

 Central line for an occultation by (102) Miriam

 (102) Miriam occults TYC 5757 9 (RA 20 51 34.710 DE -7 30 41.11)
 orbit MPC25186, diff. corr. applied to ACT star position

 Minimum geocentric distance:
 date: 1998 8 2 time: 23 56 58.UT; d=6.64",PW=344.20 deg,pi=7.95",mu=31.50"/h
 substellar point on earth (lat., long.), PA of least distance:
     -7.51     2.27   344.20

     Lat.     Long. hh:mm:ss UT  StarAlt° StarAzi°  SunAlt°  SunAzi°
     67.01    50.30 23:48:58. !      8.6    226.2      1.1     43.3
     64.16    38.98 23:49:28. !     13.8    215.7     -4.0     33.0
     62.02    31.56 23:49:58. !     17.3    208.7     -7.4     26.3
     60.23    25.75 23:50:28. !     20.1    203.1    -10.2     21.1
     58.66    20.85 23:50:59. !     22.5    198.4    -12.5     16.6
     57.24    16.53 23:51:29. !     24.4    194.0    -14.4     12.6
     55.93    12.62 23:51:59. !     26.1    190.1    -16.1      9.0
     54.72     9.01 23:52:30. !     27.6    186.3    -17.5      5.6
     53.58     5.62 23:52:60. !     28.9    182.7    -18.8      2.3
     52.52     2.42 23:53:30. !     30.0    179.2    -19.9    359.2
     51.51     -.65 23:54: 0. !     30.9    175.8    -20.8    356.2
     50.55    -3.60 23:54:31. !     31.7    172.4    -21.6    353.3
     49.64    -6.47 23:55: 1. !     32.3    169.2    -22.3    350.4
     48.76    -9.27 23:55:31. !     32.8    165.9    -22.8    347.6
     47.93   -12.02 23:56: 2. !     33.1    162.7    -23.2    344.9
     47.14   -14.73 23:56:32. !     33.3    159.6    -23.4    342.2
     46.37   -17.41 23:57: 2. !     33.4    156.5    -23.6    339.5
     45.64   -20.08 23:57:32. !     33.3    153.4    -23.6    336.8
     44.94   -22.75 23:58: 3. !     33.0    150.3    -23.5    334.1
     44.27   -25.43 23:58:33. !     32.7    147.3    -23.3    331.5
     43.64   -28.13 23:59: 3. !     32.2    144.3    -22.9    328.9
     43.03   -30.86 23:59:34. !     31.5    141.4    -22.4    326.3
     42.45   -33.64  0: 0: 4. !     30.7    138.5    -21.8    323.7
     41.90   -36.48  0: 0:34. !     29.7    135.6    -21.0    321.2
     41.38   -39.41  0: 1: 4. !     28.6    132.7    -20.0    318.6
     40.90   -42.44  0: 1:35. !     27.3    129.8    -18.9    316.0
     40.45   -45.62  0: 2: 5. !     25.7    126.9    -17.5    313.4
     40.05   -48.98  0: 2:35. !     23.9    124.0    -16.0    310.7
     39.70   -52.60  0: 3: 6. !     21.9    121.1    -14.1    307.9
     39.42   -56.57  0: 3:36. !     19.4    118.0    -11.9    305.0
     39.23   -61.10  0: 4: 6. !     16.5    114.6     -9.2    301.8
     39.19   -66.62  0: 4:36. !     12.7    110.8     -5.6    298.1
     39.54   -74.91  0: 5: 7. !      6.6    105.3       .3    292.9

Good luck for the observations!

Martin Federspiel

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Martin Federspiel                 ******** E-mail: martin@astro.unibas.ch
Astronomisches Institut           ******** oder: federspi@astro.unibas.ch
der Universitaet Basel            **** oder: federspielm@ubaclu.unibas.ch
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