IOTA/IOTA-ES occultation update for (18) Melpomene / TYC 6274-01204-1 event on 2012 Oct 09, 20:45 UT Visible from W Africa Summary ------- On 2012 Oct 09 UT, the 140 km diameter asteroid (18) Melpomene will occult a 10.2 mag star in the constellation Sagittarius for observers along a path across W Africa. In the case of an occultation, the combined light of the asteroid and the star will drop by 1.0 mag to 10.7 mag (the magnitude of the asteroid) for at most 6.2 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: 91 * date and approx. time of event: 2012 Oct 09, 20:44 - 2012 Oct 09, 20:48 UT * geocentric midpoint of event [JD]: 2456210.3647125 * magnitude of target star: 10.2 * magnitude drop [mag]: 1.0 * estimated maximum duration [s]: 6.2 * Moon: 35 % sunlit, 153° distance * Sun: 81° distance * rough path description: W Africa The occultation path -------------------- * approximate projected width [km]: 215 * 1 sigma uncertainty interval [path widths]: +/- 0.51 * 1 sigma uncertainty interval [seconds]: +/- 2.7 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .044 +/- .050) * 1 sigma uncertainty ellipse (major, minor, PA): ( .050", .044", 0° ) * approx speed of asteroid's shadow [km/s]: 22.5996 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 6274-01204-1 by 18 Melpomene on 2012 Oct 9 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 - 48 0 0 30 45 2 20 44 52 40 185 0 29 45 50 31 45 29 28 46 38 32 48 31 - 47 0 0 30 33 28 20 44 57 40 187 -1 29 34 23 31 33 47 28 35 17 32 36 41 - 46 0 0 30 22 23 20 45 1 41 188 -2 29 23 24 31 22 35 28 24 25 32 25 21 - 45 0 0 30 11 47 20 45 6 41 189 -3 29 12 55 31 11 52 28 14 2 32 14 31 - 44 0 0 30 1 42 20 45 10 41 190 -4 29 2 56 31 1 40 28 4 9 32 4 12 - 43 0 0 29 52 6 20 45 14 41 192 -5 28 53 26 30 51 58 27 54 45 31 54 23 - 42 0 0 29 43 1 20 45 19 41 193 -5 28 44 27 30 42 47 27 45 51 31 45 6 - 41 0 0 29 34 26 20 45 23 41 194 -6 28 35 57 30 34 7 27 37 27 31 36 19 - 40 0 0 29 26 22 20 45 28 40 195 -7 28 27 58 30 25 58 27 29 32 31 28 4 - 39 0 0 29 18 49 20 45 32 40 197 -8 28 20 30 30 18 20 27 22 8 31 20 21 - 38 0 0 29 11 47 20 45 36 40 198 -9 28 13 32 30 11 13 27 15 15 31 13 9 - 37 0 0 29 5 16 20 45 41 40 199 -10 28 7 5 30 4 37 27 8 52 31 6 28 - 36 0 0 28 59 16 20 45 45 40 200 -11 28 1 9 29 58 33 27 2 59 31 0 20 - 35 0 0 28 53 47 20 45 49 40 202 -12 27 55 43 29 53 1 26 57 37 30 54 44 - 34 0 0 28 48 49 20 45 54 39 203 -13 27 50 49 29 48 0 26 52 46 30 49 39 - 33 0 0 28 44 23 20 45 58 39 204 -13 27 46 26 29 43 31 26 48 25 30 45 7 - 32 0 0 28 40 29 20 46 2 39 205 -14 27 42 34 29 39 34 26 44 36 30 41 7 - 31 0 0 28 37 6 20 46 6 38 206 -15 27 39 13 29 36 8 26 41 17 30 37 39 - 30 0 0 28 34 15 20 46 11 38 207 -16 27 36 24 29 33 15 26 38 30 30 34 43 - 29 0 0 28 31 55 20 46 15 38 209 -17 27 34 6 29 30 54 26 36 13 30 32 20 - 28 0 0 28 30 7 20 46 19 37 210 -18 27 32 19 29 29 4 26 34 28 30 30 29 - 27 0 0 28 28 51 20 46 23 37 211 -19 27 31 3 29 27 47 26 33 13 30 29 11 - 26 0 0 28 28 6 20 46 27 36 212 -20 27 30 20 29 27 2 26 32 30 30 28 25 - 25 0 0 28 27 53 20 46 31 36 213 -21 27 30 7 29 26 48 26 32 17 30 28 11 - 24 0 0 28 28 12 20 46 35 35 214 -21 27 30 26 29 27 7 26 32 36 30 28 30 - 23 0 0 28 29 2 20 46 39 35 215 -22 27 31 16 29 27 58 26 33 26 30 29 21 - 22 0 0 28 30 24 20 46 43 34 216 -23 27 32 37 29 29 20 26 34 47 30 30 44 - 21 0 0 28 32 18 20 46 46 34 217 -24 27 34 30 29 31 15 26 36 39 30 32 40 - 20 0 0 28 34 43 20 46 50 33 218 -25 27 36 54 29 33 41 26 39 1 30 35 8 - 19 0 0 28 37 39 20 46 54 33 219 -26 27 39 49 29 36 39 26 41 55 30 38 8 - 18 0 0 28 41 7 20 46 57 32 219 -27 27 43 15 29 40 9 26 45 19 30 41 40 - 17 0 0 28 45 6 20 47 1 31 220 -28 27 47 12 29 44 11 26 49 14 30 45 44 - 16 0 0 28 49 37 20 47 4 31 221 -29 27 51 40 29 48 44 26 53 39 30 50 19 - 15 0 0 28 54 38 20 47 8 30 222 -29 27 56 38 29 53 48 26 58 35 30 55 27 - 14 0 0 29 0 11 20 47 11 29 223 -30 28 2 8 29 59 24 27 4 2 31 1 7 - 13 0 0 29 6 14 20 47 14 29 224 -31 28 8 8 30 5 31 27 9 58 31 7 17 - 12 0 0 29 12 48 20 47 18 28 225 -32 28 14 38 30 12 9 27 16 25 31 14 0 - 11 0 0 29 19 53 20 47 21 27 225 -33 28 21 39 30 19 18 27 23 22 31 21 13 - 10 0 0 29 27 28 20 47 24 27 226 -34 28 29 9 30 26 58 27 30 49 31 28 58 - 9 0 0 29 35 33 20 47 27 26 227 -34 28 37 10 30 35 8 27 38 45 31 37 13 - 8 0 0 29 44 9 20 47 30 25 228 -35 28 45 41 30 43 49 27 47 11 31 46 0 - 7 0 0 29 53 14 20 47 33 24 228 -36 28 54 41 30 52 59 27 56 6 31 55 16 - 6 0 0 30 2 49 20 47 35 24 229 -37 29 4 10 31 2 40 28 5 30 32 5 4 - 5 0 0 30 12 53 20 47 38 23 230 -38 29 14 9 31 12 51 28 15 23 32 15 21 - 4 0 0 30 23 27 20 47 40 22 230 -39 29 24 36 31 23 31 28 25 45 32 26 8 - 3 0 0 30 34 30 20 47 43 21 231 -39 29 35 33 31 34 40 28 36 35 32 37 25 - 2 0 0 30 46 1 20 47 45 20 232 -40 29 46 58 31 46 18 28 47 54 32 49 11 - 1 0 0 30 58 1 20 47 48 20 232 -41 29 58 51 31 58 26 28 59 40 33 1 26 0 0 0 31 10 29 20 47 50 19 233 -42 30 11 12 32 11 1 29 11 54 33 14 10 1 0 0 31 23 25 20 47 52 18 234 -42 30 24 0 32 24 5 29 24 36 33 27 22 2 0 0 31 36 49 20 47 54 17 234 -43 30 37 16 32 37 37 29 37 45 33 41 3 3 0 0 31 50 40 20 47 56 16 235 -44 30 50 59 32 51 36 29 51 20 33 55 11 4 0 0 32 4 58 20 47 58 16 235 -44 31 5 9 33 6 3 30 5 22 34 9 47 5 0 0 32 19 42 20 48 0 15 236 -45 31 19 46 33 20 56 30 19 51 34 24 51 6 0 0 32 34 53 20 48 1 14 237 -46 31 34 48 33 36 16 30 34 45 34 40 21 7 0 0 32 50 30 20 48 3 13 237 -46 31 50 16 33 52 3 30 50 4 34 56 17 8 0 0 33 6 32 20 48 4 12 238 -47 32 6 9 34 8 14 31 5 49 35 12 39 9 0 0 33 23 0 20 48 6 11 238 -48 32 22 27 34 24 52 31 21 58 35 29 27 10 0 0 33 39 52 20 48 7 10 239 -48 32 39 10 34 41 54 31 38 32 35 46 41 11 0 0 33 57 8 20 48 8 10 240 -49 32 56 17 34 59 20 31 55 29 36 4 19 12 0 0 34 14 48 20 48 9 9 240 -49 33 13 47 35 17 11 32 12 50 36 22 21 13 0 0 34 32 52 20 48 10 8 241 -50 33 31 40 35 35 25 32 30 34 36 40 47 14 0 0 34 51 18 20 48 11 7 241 -50 33 49 57 35 54 3 32 48 41 36 59 36 15 0 0 35 10 7 20 48 12 6 242 -51 34 8 35 36 13 2 33 7 9 37 18 48 16 0 0 35 29 17 20 48 12 5 243 -51 34 27 35 36 32 24 33 26 0 37 38 22 17 0 0 35 48 49 20 48 13 4 243 -51 34 46 57 36 52 7 .. .. .. 37 58 18 18 0 0 36 8 42 20 48 13 3 244 -52 35 6 39 37 12 12 .. .. .. 38 18 34 19 0 0 36 28 55 20 48 13 3 244 -52 35 26 41 37 32 36 .. .. .. 38 39 12 20 0 0 36 49 28 20 48 14 2 245 -52 35 47 3 37 53 21 .. .. .. 39 0 9 21 0 0 37 10 20 20 48 14 1 246 -53 36 7 44 38 14 25 .. .. .. .. .. .. Uncertainty in time = +/- 3 secs Prediction of 2012 Sep 27.0 Data for the target star ------------------------ * name: TYC 6274-01204-1 * constellation : Sagittarius * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 18 30 48.4378 DE: -18 49 42.742 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .043, .049 ) * V mag [mag]: 10.2 * B mag [mag]: 11.8 * Diameter [mas]: 0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (18) Melpomene approx. diameter [km]: 140 approx. diameter ["]: .098 distance from Earth [AU]: 1.96600 * orbital information: orbit source: Preston date of fit: 2012 Sep 07 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 3922 number of rejected observations: 307 time covered by the observations: 1901 Aug 14 - 2012 Aug 30 1 sigma uncertainty ellipse (major, minor, PA): 0.008, 0.007, 99° remarks: * orbital elements for (18) Melpomene : Mean anomaly = 309.82166491 deg Arg. of pericenter = 228.00019164 deg Long. of node = 150.49562620 deg Inclination = 10.12757235 deg Eccentricity = 0.21810227 Semimajor axis = 2.29564122 AU Perihelion dist = 1.79495665 AU Mag: H = 6.54, G = 0.25 Epoch of elements : MJD 56209.86500000 TDT (2012 Oct 09.865) ------ occelmnt file for Occult BEGIN ----------------------------------- 2012 Oct 9 18 Melpomene 20h 45.2m UT 10.2 18 30 48.438-18 49 42.74TYC 6274-01204-1 11.8 10.7 140 6.2 1.966 3.964 -9.45 -52.4638 -18.825 -134.53 -6.66 20.7531 0.12871 0.74680 12.57956 -2.11351 0.00528 0.00035 2000 307.0262572012 930.00000228.000192150.495626 10.1275720.21810227 2.2956412 1.7949567 6.5 5.00.25 RATE 2.8336620 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.050 0.044 0 1.51 0.050 0 0-2-2 056197.0020121009_1204-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2012 Sep 07, 22:33 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org