IOTA/IOTA-ES occultation update for (1838) Ursa / TYC 2409-00921-1 event on 2012 Aug 24, 10:00 UT Visible from W Canada, NW USA Summary ------- On 2012 Aug 24 UT, the 40 km diameter asteroid (1838) Ursa will occult a 9.4 mag star in the constellation Auriga for observers along a path across W Canada, NW USA. In the case of an occultation, the combined light of the asteroid and the star will drop by 7.3 mag to 16.7 mag (the magnitude of the asteroid) for at most 1.4 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: 41 * date and approx. time of event: 2012 Aug 24, 09:59 - 2012 Aug 24, 10:01 UT * geocentric midpoint of event [JD]: 2456163.91753333 * magnitude of target star: 9.4 * magnitude drop [mag]: 7.3 * estimated maximum duration [s]: 1.4 * Moon: 49 % sunlit, 152° distance * Sun: 65° distance * rough path description: W Canada, NW USA The occultation path -------------------- * approximate projected width [km]: 65 * 1 sigma uncertainty interval [path widths]: +/- 1.58 * 1 sigma uncertainty interval [seconds]: +/- 2.9 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .038 +/- .027) * 1 sigma uncertainty ellipse (major, minor, PA): ( .039", .025", 74° ) * approx speed of asteroid's shadow [km/s]: 29.0464 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 2409-00921-1 by 1838 Ursa on 2012 Aug 24 Centre Star Star Sun Path Limit1 Path Limit2 Error Limit1 Error Limit2 E. Longitude Latitude U.T. Alt Az Alt o ' " o ' " h m s o o o o ' " o ' " o ' " o ' " o ' " o ' " o ' " o ' " Longitude Latitude Longitude Latitude Longitude Latitude Longitude Latitude -139 51 49 30 31 52 9 59 2 6 56 -48 -141 22 46 29 45 39 -138 37 22 31 6 52 ... .. .. .. .. .. -135 30 36 32 24 13 -136 33 26 33 14 4 9 59 5 10 58 -44 -137 29 51 32 51 31 -135 40 48 33 33 58 -141 13 12 31 9 11 -133 11 55 34 24 41 -134 14 59 35 15 36 9 59 8 13 59 -42 -135 1 40 35 0 0 -133 30 13 35 29 51 -137 46 27 33 58 32 -131 18 44 36 7 43 -132 22 40 36 59 17 9 59 12 15 61 -40 -133 4 27 36 47 21 -131 42 7 37 10 19 -135 26 37 36 2 23 -129 40 52 37 40 14 -130 45 54 38 32 15 9 59 15 17 62 -38 -131 24 43 38 22 41 -130 8 0 38 41 10 -133 34 25 37 47 18 -128 13 25 39 5 31 -129 19 43 39 57 55 9 59 19 18 63 -36 -129 56 34 39 50 1 -128 43 35 40 5 16 -131 58 22 39 21 8 -126 53 39 40 25 27 -128 1 17 41 18 11 9 59 22 20 64 -34 -128 36 45 41 11 34 -127 26 25 41 24 21 -130 33 11 40 47 27 -125 39 48 41 41 13 -126 48 51 42 34 16 9 59 26 21 65 -33 -127 23 20 42 28 40 -126 14 53 42 39 28 -129 15 59 42 8 16 -124 30 40 42 53 38 -125 41 12 43 46 59 9 59 29 22 66 -31 -126 14 59 43 42 14 -125 7 53 43 51 24 -128 4 55 43 24 50 -123 25 24 44 3 18 -124 37 29 44 56 57 9 59 32 24 67 -30 -125 10 45 44 52 55 -124 4 38 45 0 42 -126 58 46 44 38 0 -122 23 22 45 10 38 -123 37 4 46 4 37 9 59 36 25 68 -29 -124 9 59 46 1 11 -123 4 32 46 7 46 -125 56 39 45 48 22 -121 24 4 46 16 0 -122 39 26 47 10 17 9 59 39 26 69 -27 -123 12 8 47 7 23 -122 7 6 47 12 56 -124 57 56 46 56 25 -120 27 7 47 19 40 -121 44 13 48 14 16 9 59 43 27 70 -26 -122 16 48 48 11 50 -121 11 58 48 16 27 -124 2 6 48 2 29 -119 32 11 48 21 50 -120 51 6 49 16 46 9 59 46 28 72 -25 -121 23 39 49 14 46 -120 18 51 49 18 32 -123 8 46 49 6 50 -118 39 1 49 22 42 -119 59 48 50 17 58 9 59 49 28 73 -24 -120 32 26 50 16 21 -119 27 30 50 19 22 -122 17 38 50 9 42 -117 47 24 50 22 24 -119 10 9 51 18 1 9 59 53 29 74 -23 -119 42 53 51 16 45 -118 37 42 51 19 4 -121 28 26 51 11 17 -116 57 8 51 21 4 -118 21 55 52 17 3 9 59 56 30 75 -22 -118 54 52 52 16 6 -117 49 17 52 17 47 -120 40 58 52 11 43 -116 8 3 52 18 50 -117 34 59 53 15 11 10 0 0 31 76 -20 -118 8 10 53 14 32 -117 2 5 53 15 37 -119 55 3 53 11 8 -115 20 2 53 15 46 -116 49 12 54 12 30 10 0 3 31 77 -19 -117 22 42 54 12 8 -116 15 59 54 12 40 -119 10 33 54 9 40 -114 32 57 54 11 58 -116 4 26 55 9 5 10 0 7 32 78 -18 -116 38 18 55 9 0 -115 30 52 55 9 0 -118 27 19 55 7 23 -113 46 40 55 7 29 -115 20 36 56 5 2 10 0 10 33 79 -17 -115 54 54 56 5 11 -114 46 36 56 4 41 -117 45 16 56 4 23 -113 1 6 56 2 25 -114 37 36 57 0 24 10 0 13 33 80 -16 -115 12 23 57 0 47 -114 3 8 56 59 49 -117 4 17 57 0 45 -112 16 9 56 56 49 -113 55 21 57 55 14 10 0 17 34 82 -15 -114 30 40 57 55 51 -113 20 21 57 54 26 -116 24 17 57 56 33 -111 31 44 57 50 44 -113 13 46 58 49 36 10 0 20 34 83 -14 -113 49 41 58 50 26 -112 38 11 58 48 35 -115 45 13 58 51 50 -110 47 45 58 44 12 -112 32 48 59 43 33 10 0 24 35 84 -14 -113 9 21 59 44 36 -111 56 33 59 42 20 -115 7 1 59 46 39 -110 4 8 59 37 17 -111 52 21 60 37 8 10 0 27 35 85 -13 -112 29 38 60 38 23 -111 15 24 60 35 42 -114 29 37 60 41 5 -109 20 49 60 30 2 -111 12 23 61 30 24 10 0 30 35 86 -12 -111 50 27 61 31 50 -110 34 39 61 28 46 -113 52 59 61 35 9 -108 37 42 61 22 27 -110 32 49 62 23 21 10 0 34 36 88 -11 -111 11 45 62 25 0 -109 54 15 62 21 32 -113 17 5 62 28 54 -107 54 44 62 14 37 -109 53 38 63 16 4 10 0 37 36 89 -10 -110 33 29 63 17 54 -109 14 9 63 14 4 -112 41 52 63 22 23 -107 11 49 63 6 32 -109 14 44 64 8 34 10 0 41 36 90 -9 -109 55 36 64 10 35 -108 34 15 64 6 22 -112 7 19 64 15 38 -106 28 54 63 58 14 -108 36 6 65 0 53 10 0 44 37 91 -8 -109 18 5 65 3 5 -107 54 32 64 58 30 -111 33 25 65 8 41 -105 45 53 64 49 46 -107 57 40 65 53 3 10 0 48 37 93 -7 -108 40 51 65 55 25 -107 14 55 65 50 29 -111 0 9 66 1 34 -105 2 41 65 41 10 -107 19 23 66 45 6 10 0 51 37 94 -7 -108 3 53 66 47 39 -106 35 21 66 42 21 -110 27 30 66 54 19 -104 19 14 66 32 26 -106 41 12 67 37 3 10 0 54 37 95 -6 -107 27 8 67 39 46 -105 55 45 67 34 7 -109 55 29 67 46 59 -103 35 24 67 23 36 -106 3 3 68 28 57 10 0 58 37 96 -5 -106 50 33 68 31 51 -105 16 4 68 25 50 -109 24 5 68 39 34 -102 51 6 68 14 43 -105 24 53 69 20 48 10 1 1 38 98 -4 -106 14 7 69 23 53 -104 36 13 69 17 31 -108 53 21 69 32 7 -102 6 12 69 5 47 -104 46 38 70 12 40 10 1 5 38 99 -3 -105 37 46 70 15 55 -103 56 7 70 9 11 -108 23 17 70 24 40 -101 20 34 69 56 50 -104 8 15 71 4 32 10 1 8 38 100 -3 -105 1 28 71 7 58 -103 15 42 71 0 53 -107 53 56 71 17 13 -100 34 4 70 47 53 -103 29 38 71 56 28 10 1 11 38 102 -2 -104 25 10 72 0 5 -102 34 50 71 52 37 -107 25 20 72 9 50 - 99 46 30 71 38 59 -102 50 43 72 48 28 10 1 15 38 103 -1 -103 48 49 72 52 16 -101 53 25 72 44 26 -106 57 36 73 2 32 - 98 57 41 72 30 7 -102 11 24 73 40 35 10 1 18 38 104 0 -103 12 23 73 44 33 -101 11 18 73 36 20 -106 30 48 73 55 19 - 98 7 20 73 21 21 Uncertainty in time = +/- 3 secs Prediction of 2012 Jul 8.0 Data for the target star ------------------------ * name: TYC 2409-00921-1 * constellation : Auriga * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 05 43 11.0268 DE: +32 16 59.422 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .016, .016 ) * V mag [mag]: 9.4 * B mag [mag]: 9.7 * Diameter [mas]: 0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (1838) Ursa approx. diameter [km]: 40 approx. diameter ["]: .016 distance from Earth [AU]: 3.45300 * orbital information: orbit source: Preston date of fit: 2012 Jul 07 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 908 number of rejected observations: 12 time covered by the observations: 1951 Apr 09 - 2012 Feb 02 1 sigma uncertainty ellipse (major, minor, PA): 0.036, 0.020, 71° remarks: * orbital elements for (1838) Ursa : Mean anomaly = 333.59662466 deg Arg. of pericenter = 54.12419470 deg Long. of node = 44.27318311 deg Inclination = 21.98638604 deg Eccentricity = 0.01841658 Semimajor axis = 3.22100313 AU Perihelion dist = 3.16168328 AU Mag: H = 10.69, G = 0.15 Epoch of elements : MJD 56163.41700000 TDT (2012 Aug 24.417) ------ occelmnt file for Occult BEGIN ----------------------------------- 2012 Aug 24 1838 Ursa 10h 1.2m UT 9.4 5 43 11.027 32 16 59.42TYC 2409-00921-1 9.7 16.7 40 1.4 3.453 3.093 14.32 -37.6050 32.280 30.26 10.89 10.0208 -0.26968 0.73887 15.40079 5.62128 -0.00520 0.00021 2000 333.0140362012 821.00000 54.124195 44.273183 21.9863860.01841658 3.2210031 3.161683310.6 5.00.15 RATE 1.7049720 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.039 0.025 74 2.58 0.025 0 0-2 2 056116.0020120824_0921-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2012 Jul 07, 23:50 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org