IOTA/IOTA-ES occultation update for (257) Silesia / UCAC2 20938530 event on 2008 Oct 13, 01:04 UT Visible from Venezuela, Colombia Summary ------- On 2008 Oct 13 UT, the 73 km diameter asteroid (257) Silesia will occult a 11.9 mag star in the constellation Sagittarius for observers along a path across Venezuela, Colombia. In the case of an occultation, the combined light of the asteroid and the star will drop by 3.7 mag to 15.6 mag (the magnitude of the asteroid) for at most 3.2 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: 39 * date and approx. time of event: 2008 Oct 13, 01:05 - 2008 Oct 13, 01:08 UT * midpoint of event [JD]: 2454752.54465833 * magnitude of target star: 11.9 * magnitude drop [mag]: 3.7 * estimated maximum duration [s]: 3.2 * Moon: 96 % sunlit, 82° distance * Sun: 76° distance * rough path description: Venezuela, Colombia The occultation path -------------------- * approximate projected width [km]: 77 * 1 sigma uncertainty interval [path widths]: +/- 1.71 * 1 sigma uncertainty interval [seconds]: +/- 5.0 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .051 +/- .050) * 1 sigma uncertainty ellipse (major, minor, PA): ( .051", .050", 90° ) * approx speed of asteroid's shadow [km/s]: 22.5871 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of UCAC2 20938530 by 257 Silesia on 2008 Oct 13 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 -109 0 0 - 5 31 3 1 5 31 65 209 0 - 5 52 28 - 5 9 36 - 7 5 21 - 3 55 49 -108 0 0 - 5 17 44 1 5 36 65 210 -1 - 5 39 12 - 4 56 15 - 6 52 13 - 3 42 21 -107 0 0 - 5 3 55 1 5 41 64 212 -2 - 5 25 24 - 4 42 23 - 6 38 33 - 3 28 20 -106 0 0 - 4 49 35 1 5 46 63 213 -3 - 5 11 6 - 4 28 0 - 6 24 23 - 3 13 49 -105 0 0 - 4 34 43 1 5 51 62 215 -4 - 4 56 18 - 4 13 6 - 6 9 43 - 2 58 47 -104 0 0 - 4 19 22 1 5 56 62 216 -5 - 4 40 59 - 3 57 42 - 5 54 33 - 2 43 14 -103 0 0 - 4 3 30 1 6 1 61 217 -6 - 4 25 9 - 3 41 48 - 5 38 52 - 2 27 10 -102 0 0 - 3 47 8 1 6 5 60 218 -7 - 4 8 50 - 3 25 23 - 5 22 42 - 2 10 36 -101 0 0 - 3 30 15 1 6 10 59 219 -8 - 3 52 0 - 3 8 28 - 5 6 1 - 1 53 32 -100 0 0 - 3 12 53 1 6 15 58 220 -9 - 3 34 41 - 2 51 3 - 4 48 51 - 1 35 57 - 99 0 0 - 2 55 1 1 6 20 57 221 -10 - 3 16 52 - 2 33 8 - 4 31 12 - 1 17 52 - 98 0 0 - 2 36 40 1 6 24 56 222 -12 - 2 58 33 - 2 14 44 - 4 13 3 - 0 59 18 - 97 0 0 - 2 17 49 1 6 29 56 222 -13 - 2 39 45 - 1 55 50 - 3 54 25 - 0 40 14 - 96 0 0 - 1 58 29 1 6 33 55 223 -14 - 2 20 29 - 1 36 27 - 3 35 18 - 0 20 41 - 95 0 0 - 1 38 41 1 6 38 54 224 -15 - 2 0 43 - 1 16 36 - 3 15 43 - 0 0 39 - 94 0 0 - 1 18 24 1 6 42 53 224 -16 - 1 40 29 - 0 56 15 - 2 55 39 0 19 52 - 93 0 0 - 0 57 38 1 6 47 52 225 -17 - 1 19 47 - 0 35 27 - 2 35 7 0 40 51 - 92 0 0 - 0 36 25 1 6 51 51 226 -18 - 0 58 36 - 0 14 10 - 2 14 7 1 2 19 - 91 0 0 - 0 14 44 1 6 56 50 226 -19 - 0 36 59 0 7 34 - 1 52 40 1 24 14 - 90 0 0 0 7 24 1 7 0 49 227 -20 - 0 14 54 0 29 45 - 1 30 46 1 46 36 - 89 0 0 0 29 59 1 7 4 48 227 -21 0 7 38 0 52 23 - 1 8 24 2 9 26 - 88 0 0 0 53 1 1 7 8 47 228 -22 0 30 37 1 15 28 - 0 45 37 2 32 42 - 87 0 0 1 16 29 1 7 12 46 228 -23 0 54 1 1 38 59 - 0 22 23 2 56 24 - 86 0 0 1 40 22 1 7 16 45 228 -24 1 17 52 2 2 56 0 1 17 3 20 32 - 85 0 0 2 4 41 1 7 20 44 229 -25 1 42 7 2 27 18 0 25 21 3 45 5 - 84 0 0 2 29 25 1 7 24 43 229 -26 2 6 48 2 52 5 0 49 51 4 10 3 - 83 0 0 2 54 32 1 7 28 42 230 -27 2 31 52 3 17 16 1 14 45 4 35 25 - 82 0 0 3 20 4 1 7 32 41 230 -28 2 57 21 3 42 51 1 40 2 5 1 11 - 81 0 0 3 45 59 1 7 36 40 230 -30 3 23 12 4 8 49 2 5 43 5 27 20 - 80 0 0 4 12 16 1 7 39 39 231 -31 3 49 27 4 35 9 2 31 47 5 53 51 - 79 0 0 4 38 56 1 7 43 37 231 -32 4 16 3 5 1 52 2 58 13 6 20 45 - 78 0 0 5 5 57 1 7 46 36 231 -33 4 43 1 5 28 56 3 25 0 6 48 0 - 77 0 0 5 33 19 1 7 50 35 231 -34 5 10 20 5 56 21 3 52 9 7 15 35 - 76 0 0 6 1 1 1 7 53 34 232 -35 5 37 59 6 24 6 4 19 38 7 43 31 - 75 0 0 6 29 2 1 7 56 33 232 -36 6 5 57 6 52 10 4 47 26 8 11 46 - 74 0 0 6 57 23 1 7 59 32 232 -37 6 34 15 7 20 34 5 15 34 8 40 19 - 73 0 0 7 26 1 1 8 2 31 233 -38 7 2 50 7 49 15 5 44 0 9 9 11 - 72 0 0 7 54 57 1 8 5 30 233 -39 7 31 43 8 18 14 6 12 44 9 38 19 - 71 0 0 8 24 9 1 8 8 29 233 -40 8 0 53 8 47 29 6 41 44 10 7 44 - 70 0 0 8 53 37 1 8 11 28 233 -41 8 30 18 9 16 59 7 11 0 10 37 24 - 69 0 0 9 23 20 1 8 13 27 234 -42 8 59 59 9 46 45 7 40 32 11 7 18 - 68 0 0 9 53 17 1 8 16 26 234 -43 9 29 54 10 16 45 8 10 19 11 37 27 - 67 0 0 10 23 28 1 8 18 24 234 -44 10 0 2 10 46 58 8 40 19 12 7 49 - 66 0 0 10 53 51 1 8 21 23 234 -45 10 30 23 11 17 23 9 10 31 12 38 22 - 65 0 0 11 24 26 1 8 23 22 235 -46 11 0 55 11 48 0 9 40 56 13 9 7 - 64 0 0 11 55 11 1 8 25 21 235 -47 11 31 38 12 18 48 10 11 32 13 40 2 - 63 0 0 12 26 6 1 8 27 20 235 -48 12 2 31 12 49 45 10 42 18 14 11 7 - 62 0 0 12 57 10 1 8 29 19 235 -49 12 33 33 13 20 51 11 13 14 14 42 19 - 61 0 0 13 28 23 1 8 31 18 236 -50 13 4 44 13 52 5 11 44 18 15 13 40 - 60 0 0 13 59 42 1 8 33 17 236 -51 13 36 1 14 23 26 12 15 29 15 45 7 - 59 0 0 14 31 7 1 8 34 16 236 -52 14 7 25 14 54 53 12 46 48 16 16 39 - 58 0 0 15 2 37 1 8 36 15 237 -53 14 38 54 15 26 25 13 18 11 16 48 17 - 57 0 0 15 34 12 1 8 37 13 237 -54 15 10 27 15 58 1 13 49 40 17 19 58 - 56 0 0 16 5 50 1 8 38 12 237 -54 15 42 4 16 29 40 14 21 12 17 51 41 - 55 0 0 16 37 30 1 8 40 11 237 -55 16 13 43 17 1 22 14 52 48 18 23 27 - 54 0 0 17 9 12 1 8 41 10 238 -56 16 45 23 17 33 4 15 24 25 18 55 13 - 53 0 0 17 40 54 1 8 42 9 238 -57 17 17 4 18 4 47 15 56 3 19 26 59 - 52 0 0 18 12 35 1 8 42 8 238 -58 17 48 45 18 36 29 16 27 41 19 58 44 - 51 0 0 18 44 15 1 8 43 7 239 -59 18 20 24 19 8 10 16 59 18 20 30 27 - 50 0 0 19 15 53 1 8 44 6 239 -59 18 52 2 19 39 48 17 30 54 21 2 7 - 49 0 0 19 47 27 1 8 44 5 239 -60 19 23 36 20 11 23 18 2 26 21 33 43 - 48 0 0 20 18 57 1 8 45 4 240 -61 19 55 5 20 42 53 18 33 55 22 5 14 - 47 0 0 20 50 22 1 8 45 3 240 -61 20 26 30 21 14 18 19 5 20 22 36 40 - 46 0 0 21 21 41 1 8 45 2 240 -62 20 57 49 21 45 37 .. .. .. 23 7 58 - 45 0 0 21 52 53 1 8 45 0 241 -63 21 29 1 22 16 49 .. .. .. .. .. .. Uncertainty in time = +/- 6 secs [Prediction of 2008 Sep 5.0] Data for the target star ------------------------ * name: UCAC2 20938530 * constellation : Sagittarius * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 18 24 42.2119 DE: -26 45 53.469 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .048, .048 ) * V mag [mag]: 11.9 * B mag [mag]: 0.0 * Apparent position with proper motion RA(deg): 276.3147069594 DE(deg): -26.7617560609 * Equation of equinoxes (radians) : 0.000048219275777 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (257) Silesia approx. diameter [km]: 73 approx. diameter ["]: .029 distance from Earth [AU]: 3.41900 * orbital information: orbit source: Preston date of fit: 2008 Sep 04 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 872 number of rejected observations: 125 time covered by the observations: 1902 Mar 06 - 2008 Aug 21 1 sigma uncertainty ellipse (major, minor, PA): 0.016, 0.011, 90° remarks: * orbital elements for (257) Silesia : Mean anomaly = 243.56167565 deg Arg. of pericenter = 25.30786121 deg Long. of node = 34.63196927 deg Inclination = 3.63314423 deg Eccentricity = 0.11451142 Semimajor axis = 3.12598684 AU Perihelion dist = 2.76802566 AU Mag: H = 9.30, G = 0.15 Epoch of elements : MJD 54752.04500000 TDT (2008 Oct 13.045) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 Oct 13 257 Silesia 1h 4.3m UT 11.9 18 24 42.212-26 45 53.47UCAC2 20938530 0.0 15.6 73 3.2 3.419 2.437 3.22 -121.8719 -26.766 160.49 -7.85 1.0718 -0.03259 0.32603 12.68732 1.25051 0.00567 0.00015 2000 243.19699220081011.00000 25.307861 34.631969 3.6331440.11451142 3.1259868 2.7680256 9.5 5.00.15 RATE 1.7832960 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.051 0.050 90 2.71 0.050 0 54714.5020081013_938530 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 Sep 11, 16:57 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org