IOTA/IOTA-ES occultation update for (2333) Porthan / TYC 6181-00621-1 event on 2008 May 12, 08:43 UT Visible from Caribbean, Central America Summary ------- On 2008 May 12 UT, the 22 km diameter asteroid (2333) Porthan will occult a 9.8 mag star in the constellation Libra for observers along a path across Caribbean, Central America. In the case of an occultation, the combined light of the asteroid and the star will drop by 5.0 mag to 14.8 mag (the magnitude of the asteroid) for at most 1.8 seconds. This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Alice Monet, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: UCAC. The event at a glimpse ---------------------- * Rank: 19 * date and approx. time of event: 2008 May 12, 08:36 - 2008 May 12, 08:51 UT * magnitude of target star: 9.8 * magnitude drop [mag]: 5.0 * estimated maximum duration [s]: 1.8 * Moon: 53 % sunlit, 86° distance * Sun: 176° distance * rough path description: Caribbean, Central America The occultation path -------------------- * approximate projected width [km]: 26 * 1 sigma uncertainty interval [path widths]: +/- 3.47 * 1 sigma uncertainty interval [seconds]: +/- 7.7 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .087 +/- .065) * 1 sigma uncertainty ellipse (major, minor, PA): ( .092", .057", 116° ) * approx speed of asteroid's shadow [km/s]: 12.0692 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 6181-00621-1 by 2333 Porthan on 2008 May 12 Centre Star Star Sun Path Limits Error Limits E. Longitude Latitude U.T. Alt Az Alt Limit 1 Limit 2 Limit 3 Limit 4 o ' " o ' " h m s o o o o ' " o ' " o ' " o ' " Latitude Latitude Latitude Latitude 146 0 0 26 17 56 8 51 11 1 114 0 26 25 34 26 10 17 27 18 57 .. .. .. 147 0 0 25 53 43 8 51 11 2 115 -1 26 1 21 25 46 5 26 54 40 .. .. .. 148 0 0 25 29 36 8 51 11 3 115 -2 25 37 14 25 21 59 26 30 29 .. .. .. 149 0 0 25 5 37 8 51 10 4 116 -3 25 13 14 24 58 0 26 6 24 .. .. .. 150 0 0 24 41 44 8 51 9 5 116 -4 24 49 21 24 34 8 25 42 27 .. .. .. 151 0 0 24 18 0 8 51 8 6 117 -5 24 25 35 24 10 24 25 18 37 23 18 4 152 0 0 23 54 24 8 51 7 7 117 -6 24 1 59 23 46 49 24 54 55 22 54 33 153 0 0 23 30 57 8 51 6 8 117 -7 23 38 31 23 23 23 24 31 23 22 31 11 154 0 0 23 7 40 8 51 5 9 118 -8 23 15 13 23 0 7 24 8 0 22 8 0 155 0 0 22 44 33 8 51 3 10 118 -9 22 52 6 22 37 1 23 44 48 21 44 59 156 0 0 22 21 37 8 51 1 11 119 -10 22 29 9 22 14 6 23 21 46 21 22 9 157 0 0 21 58 53 8 50 59 11 119 -11 22 6 24 21 51 22 22 58 56 20 59 30 158 0 0 21 36 21 8 50 57 12 119 -12 21 43 51 21 28 51 22 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244 -6 29 3 26 28 48 4 29 57 6 .. .. .. - 57 0 0 29 20 12 8 36 1 2 244 -5 29 27 54 29 12 31 30 21 37 .. .. .. - 56 0 0 29 44 41 8 36 1 1 245 -4 29 52 23 29 36 59 30 46 8 .. .. .. Uncertainty in time = +/- 9 secs [Prediction of 2008 May 8.0] Data for the target star ------------------------ * name: TYC 6181-00621-1 * constellation : Libra * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 15 08 50.8935 DE: -21 31 12.640 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .022, .024 ) * V mag [mag]: 9.8 * B mag [mag]: 10.2 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (2333) Porthan approx. diameter [km]: 22 approx. diameter ["]: .019 distance from Earth [AU]: 1.60800 * orbital information: orbit source: Preston date of fit: 2008 May 07 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 534 number of rejected observations: 23 time covered by the observations: 1943 Mar 03 - 2008 Apr 19 1 sigma uncertainty ellipse (major, minor, PA): 0.090, 0.052, 117° remarks: * orbital elements for (2333) Porthan : Mean anomaly = 77.70832183 deg Arg. of pericenter = 97.77969760 deg Long. of node = 40.25903530 deg Inclination = 11.92664679 deg Eccentricity = 0.13643428 Semimajor axis = 2.64545499 AU Perihelion dist = 2.28452426 AU Mag: H = 11.76, G = 0.15 Epoch of elements : MJD 54598.36400000 TDT (2008 May 12.364) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 May 12 2333 Porthan 8h 43.6m UT 9.8 15 8 50.894-21 31 12.64TYC 6181-00621-1 10.2 14.8 22 1.8 1.608 -2.668 -1.24 -134.1847 -21.519 48.19 18.27 8.7267 -0.01691 0.50649 -6.80844 -0.22648 0.00024 0.00031 2000 75.7924452008 5 4.00000 97.779698 40.259035 11.9266470.13643428 2.6454550 2.284524211.5 5.00.15 RATE 2.2906230 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.092 0.057 116 4.47 0.066 0 54594.5020080512_0621-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 May 08, 03:04 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org