IOTA/IOTA-ES occultation update for (2154) Underhill / TYC 2421-00409-1 event on 2012 Sep 30, 00:33 UT Visible from Africa Summary ------- On 2012 Sep 30 UT, the 21 km diameter asteroid (2154) Underhill will occult a 9.8 mag star in the constellation Auriga for observers along a path across Africa. In the case of an occultation, the combined light of the asteroid and the star will drop by 7.6 mag to 17.4 mag (the magnitude of the asteroid) for at most 1.2 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: 15 * date and approx. time of event: 2012 Sep 30, 00:27 - 2012 Sep 30, 00:32 UT * geocentric midpoint of event [JD]: 2456200.52307917 * magnitude of target star: 9.8 * magnitude drop [mag]: 7.6 * estimated maximum duration [s]: 1.2 * Moon: 100 % sunlit, 90° distance * Sun: 91° distance * rough path description: Africa The occultation path -------------------- * approximate projected width [km]: 23 * 1 sigma uncertainty interval [path widths]: +/- 4.61 * 1 sigma uncertainty interval [seconds]: +/- 4.5 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .061 +/- .060) * 1 sigma uncertainty ellipse (major, minor, PA): ( .061", .060", 92° ) * approx speed of asteroid's shadow [km/s]: 18.0520 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 2421-00409-1 by 2154 Underhill on 2012 Sep 30 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 12 0 0 -29 22 5 0 27 57 1 53 -52 -29 29 57 -29 14 14 -30 42 54 .. .. .. 13 0 0 -28 42 27 0 27 57 2 52 -52 -28 50 18 -28 34 36 -30 3 14 .. .. .. 14 0 0 -28 2 36 0 27 57 3 52 -52 -28 10 27 -27 54 45 -29 23 21 .. .. .. 15 0 0 -27 22 34 0 27 58 4 51 -52 -27 30 25 -27 14 44 -28 43 16 .. .. .. 16 0 0 -26 42 23 0 27 58 5 51 -52 -26 50 13 -26 34 33 -28 3 1 -25 22 50 17 0 0 -26 2 3 0 27 59 7 50 -51 -26 9 53 -25 54 14 -27 22 37 -24 42 35 18 0 0 -25 21 38 0 28 0 8 50 -51 -25 29 27 -25 13 49 -26 42 5 -24 2 14 19 0 0 -24 41 7 0 28 1 9 49 -51 -24 48 56 -24 33 18 -26 1 28 -23 21 49 20 0 0 -24 0 32 0 28 2 10 49 -51 -24 8 21 -23 52 45 -25 20 47 -22 41 22 21 0 0 -23 19 56 0 28 4 11 49 -50 -23 27 44 -23 12 9 -24 40 3 -22 0 53 22 0 0 -22 39 20 0 28 5 12 48 -50 -22 47 6 -22 31 34 -23 59 18 -21 20 25 23 0 0 -21 58 44 0 28 7 13 48 -50 -22 6 30 -21 50 59 -23 18 33 -20 39 58 24 0 0 -21 18 11 0 28 9 15 47 -49 -21 25 56 -21 10 27 -22 37 51 -19 59 35 25 0 0 -20 37 43 0 28 11 16 47 -49 -20 45 27 -20 30 0 -21 57 12 -19 19 17 26 0 0 -19 57 21 0 28 13 17 47 -48 -20 5 3 -19 49 38 -21 16 38 -18 39 5 27 0 0 -19 17 5 0 28 15 18 46 -48 -19 24 47 -19 9 24 -20 36 11 -17 59 1 28 0 0 -18 36 59 0 28 18 19 46 -47 -18 44 40 -18 29 19 -19 55 53 -17 19 7 29 0 0 -17 57 3 0 28 21 20 45 -47 -18 4 43 -17 49 25 -19 15 44 -16 39 23 30 0 0 -17 17 20 0 28 24 21 45 -46 -17 24 57 -17 9 42 -18 35 47 -15 59 52 31 0 0 -16 37 49 0 28 27 23 45 -45 -16 45 26 -16 30 13 -17 56 2 -15 20 35 32 0 0 -15 58 33 0 28 30 24 44 -45 -16 6 9 -15 50 59 -17 16 32 -14 41 33 33 0 0 -15 19 34 0 28 33 25 44 -44 -15 27 8 -15 12 1 -16 37 18 -14 2 48 34 0 0 -14 40 52 0 28 36 26 43 -43 -14 48 24 -14 33 20 -15 58 21 -13 24 21 35 0 0 -14 2 29 0 28 40 27 43 -43 -14 10 0 -13 54 59 -15 19 42 -12 46 13 36 0 0 -13 24 26 0 28 44 28 43 -42 -13 31 56 -13 16 58 -14 41 24 -12 8 26 37 0 0 -12 46 45 0 28 48 29 42 -41 -12 54 13 -12 39 18 -14 3 26 -11 31 0 38 0 0 -12 9 27 0 28 52 31 42 -40 -12 16 53 -12 2 1 -13 25 52 -10 53 58 39 0 0 -11 32 32 0 28 56 32 41 -39 -11 39 57 -11 25 8 -12 48 40 -10 17 19 40 0 0 -10 56 3 0 29 0 33 41 -39 -11 3 26 -10 48 41 -12 11 54 - 9 41 6 41 0 0 -10 20 0 0 29 4 34 41 -38 -10 27 21 -10 12 39 -11 35 33 - 9 5 20 42 0 0 - 9 44 24 0 29 9 35 40 -37 - 9 51 43 - 9 37 5 -10 59 40 - 8 30 0 43 0 0 - 9 9 16 0 29 13 36 40 -36 - 9 16 34 - 9 1 58 -10 24 15 - 7 55 9 44 0 0 - 8 34 37 0 29 18 37 39 -35 - 8 41 53 - 8 27 21 - 9 49 18 - 7 20 48 45 0 0 - 8 0 28 0 29 23 38 39 -34 - 8 7 43 - 7 53 14 - 9 14 52 - 6 46 56 46 0 0 - 7 26 50 0 29 28 39 38 -33 - 7 34 3 - 7 19 38 - 8 40 57 - 6 13 35 47 0 0 - 6 53 44 0 29 33 40 38 -32 - 7 0 56 - 6 46 34 - 8 7 33 - 5 40 46 48 0 0 - 6 21 11 0 29 38 41 37 -31 - 6 28 20 - 6 14 2 - 7 34 42 - 5 8 30 49 0 0 - 5 49 11 0 29 43 42 37 -31 - 5 56 18 - 5 42 4 - 7 2 24 - 4 36 47 50 0 0 - 5 17 44 0 29 49 43 36 -30 - 5 24 50 - 5 10 39 - 6 30 40 - 4 5 37 51 0 0 - 4 46 53 0 29 54 44 36 -29 - 4 53 57 - 4 39 49 - 5 59 31 - 3 35 3 52 0 0 - 4 16 36 0 29 59 45 35 -28 - 4 23 38 - 4 9 34 - 5 28 57 - 3 5 3 53 0 0 - 3 46 55 0 30 5 46 34 -27 - 3 53 56 - 3 39 55 - 4 58 58 - 2 35 39 54 0 0 - 3 17 50 0 30 11 47 34 -26 - 3 24 49 - 3 10 51 - 4 29 37 - 2 6 50 55 0 0 - 2 49 22 0 30 16 48 33 -25 - 2 56 20 - 2 42 25 - 4 0 52 - 1 38 39 56 0 0 - 2 21 31 0 30 22 49 32 -24 - 2 28 27 - 2 14 36 - 3 32 44 - 1 11 4 57 0 0 - 1 54 18 0 30 28 50 31 -23 - 2 1 12 - 1 47 24 - 3 5 14 - 0 44 7 58 0 0 - 1 27 43 0 30 34 51 30 -22 - 1 34 35 - 1 20 50 - 2 38 22 - 0 17 47 59 0 0 - 1 1 45 0 30 40 52 30 -21 - 1 8 37 - 0 54 55 - 2 12 9 0 7 54 60 0 0 - 0 36 27 0 30 46 53 29 -20 - 0 43 16 - 0 29 37 - 1 46 35 0 32 58 61 0 0 - 0 11 47 0 30 52 54 28 -19 - 0 18 35 - 0 4 59 - 1 21 39 0 57 22 62 0 0 0 12 14 0 30 58 55 27 -18 0 5 27 0 19 0 - 0 57 23 1 21 8 63 0 0 0 35 35 0 31 4 55 26 -17 0 28 50 0 42 20 - 0 33 47 1 44 15 64 0 0 0 58 18 0 31 10 56 25 -16 0 51 34 1 5 1 - 0 10 50 2 6 43 65 0 0 1 20 20 0 31 17 57 23 -15 1 13 37 1 27 2 0 11 27 2 28 32 66 0 0 1 41 43 0 31 23 58 22 -14 1 35 1 1 48 23 0 33 3 2 49 41 67 0 0 2 2 25 0 31 29 58 21 -13 1 55 45 2 9 5 0 54 0 3 10 10 68 0 0 2 22 28 0 31 35 59 20 -12 2 15 49 2 29 6 1 14 16 3 30 0 69 0 0 2 41 51 0 31 42 60 18 -11 2 35 13 2 48 28 1 33 51 3 49 10 70 0 0 3 0 33 0 31 48 60 17 -10 2 53 57 3 7 9 1 52 46 4 7 40 71 0 0 3 18 35 0 31 54 61 15 -9 3 12 0 3 25 10 2 11 1 4 25 31 72 0 0 3 35 57 0 32 1 61 13 -8 3 29 23 3 42 31 2 28 34 4 42 41 73 0 0 3 52 39 0 32 7 62 12 -7 3 46 6 3 59 11 2 45 27 4 59 12 74 0 0 4 8 40 0 32 13 62 10 -6 4 2 9 4 15 12 3 1 39 5 15 3 75 0 0 4 24 1 0 32 20 63 8 -5 4 17 31 4 30 32 3 17 11 5 30 13 76 0 0 4 38 42 0 32 26 63 6 -4 4 32 12 4 45 11 3 32 2 5 44 44 77 0 0 4 52 42 0 32 33 63 5 -3 4 46 14 4 59 11 3 46 12 5 58 35 78 0 0 5 6 3 0 32 39 64 3 -2 4 59 35 5 12 30 3 59 41 6 11 46 79 0 0 5 18 42 0 32 45 64 1 -1 5 12 15 5 25 9 4 12 30 6 24 18 Uncertainty in time = +/- 5 secs Prediction of 2012 Aug 7.0 Data for the target star ------------------------ * name: TYC 2421-00409-1 * constellation : Auriga * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 06 26 02.4820 DE: +31 25 04.373 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .024, .034 ) * V mag [mag]: 9.8 * B mag [mag]: 11.5 * Diameter [mas]: 0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (2154) Underhill approx. diameter [km]: 21 approx. diameter ["]: .013 distance from Earth [AU]: 2.16100 * orbital information: orbit source: Preston date of fit: 2012 Aug 06 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 888 number of rejected observations: 13 time covered by the observations: 1958 Apr 08 - 2011 Nov 28 1 sigma uncertainty ellipse (major, minor, PA): 0.056, 0.049, 92° remarks: * orbital elements for (2154) Underhill : Mean anomaly = 320.58994274 deg Arg. of pericenter = 119.61881676 deg Long. of node = 0.92543368 deg Inclination = 7.74603902 deg Eccentricity = 0.12387510 Semimajor axis = 2.63756885 AU Perihelion dist = 2.31083974 AU Mag: H = 12.77, G = 0.15 Epoch of elements : MJD 56200.02300000 TDT (2012 Sep 30.023) ------ occelmnt file for Occult BEGIN ----------------------------------- 2012 Sep 30 2154 Underhill 0h 33.2m UT 9.8 6 26 2.482 31 25 4.37TYC 2421-00409-1 11.5 17.4 21 1.2 2.161 3.190 7.19 79.0330 31.415 169.19 -2.88 0.5539 0.07327 -0.42640 10.03488 1.76586 -0.00554 0.00023 2000 318.2837482012 920.00000119.618817 0.925434 7.7460390.12387510 2.6375689 2.310839712.7 5.00.15 RATE 2.3009030 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.061 0.060 92 5.61 0.062 0 0 0 3 056146.0020120930_0409-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2012 Aug 06, 21:16 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org