IOTA/IOTA-ES occultation update for (20) Massalia / 2UCAC 22751214 event on 2008 Apr 01, 02:54 UT Visible from Argentina Summary ------- On 2008 Apr 01 UT, the 146 km diameter asteroid (20) Massalia will occult a 11.7 mag star in the constellation Sagittarius for observers along a path across Argentina. In the case of an occultation, the combined light of the asteroid and the star will drop by 0.6 mag to 11.3 mag (the magnitude of the asteroid) for at most 17.4 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: 99 * date and approx. time of event: 2008 Apr 01, 02:45 - 2008 Apr 01, 02:56 UT * magnitude of target star: 11.7 * magnitude drop [mag]: 0.6 * estimated maximum duration [s]: 17.4 * Moon: 29 % sunlit, 40° distance * Sun: 105° distance * rough path description: Argentina The occultation path -------------------- * approximate projected width [km]: 202 * 1 sigma uncertainty interval [path widths]: +/- 0.27 * 1 sigma uncertainty interval [seconds]: +/- 6.9 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .038 +/- .024) * 1 sigma uncertainty ellipse (major, minor, PA): ( .038", .024", 90° ) * approx speed of asteroid's shadow [km/s]: 8.3496 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of 2UCAC 22751214 by 20 Massalia on 2008 Apr 1 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 - 75 0 0 -41 20 2 2 45 20 1 120 -42 -42 25 54 -40 15 34 -43 2 5 .. .. .. - 74 0 0 -41 47 24 2 45 20 1 120 -42 -42 53 24 -40 42 48 -43 29 41 -40 8 27 - 73 0 0 -42 14 47 2 45 21 2 119 -43 -43 20 56 -41 10 3 -43 57 17 -40 35 39 - 72 0 0 -42 42 12 2 45 22 3 118 -43 -43 48 28 -41 37 20 -44 24 54 -41 2 52 - 71 0 0 -43 9 35 2 45 23 4 118 -43 -44 16 0 -42 4 37 -44 52 29 -41 30 5 - 70 0 0 -43 36 58 2 45 24 5 117 -43 -44 43 29 -42 31 53 -45 20 3 -41 57 18 - 69 0 0 -44 4 19 2 45 26 6 116 -43 -45 10 56 -42 59 7 -45 47 34 -42 24 29 - 68 0 0 -44 31 36 2 45 27 7 116 -43 -45 38 20 -43 26 19 -46 15 0 -42 51 38 - 67 0 0 -44 58 50 2 45 29 8 115 -44 -46 5 39 -43 53 28 -46 42 23 -43 18 44 - 66 0 0 -45 25 59 2 45 32 8 114 -44 -46 32 53 -44 20 32 -47 9 39 -43 45 45 - 65 0 0 -45 53 2 2 45 34 9 113 -44 -47 0 0 -44 47 31 -47 36 49 -44 12 42 - 64 0 0 -46 19 58 2 45 37 10 113 -44 -47 27 0 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-6 -67 36 41 -65 46 10 -68 7 8 -65 16 54 45 0 0 -66 37 39 2 55 20 46 344 -5 -67 33 25 -65 42 44 -68 3 54 -65 13 26 46 0 0 -66 34 3 2 55 25 46 343 -5 -67 29 54 -65 39 4 -68 0 26 -65 9 43 47 0 0 -66 30 12 2 55 31 45 342 -4 -67 26 8 -65 35 8 -67 56 44 -65 5 44 48 0 0 -66 26 6 2 55 36 45 340 -4 -67 22 9 -65 30 57 -67 52 47 -65 1 30 49 0 0 -66 21 46 2 55 42 45 339 -3 -67 17 54 -65 26 31 -67 48 36 -64 57 1 50 0 0 -66 17 11 2 55 47 45 337 -3 -67 13 25 -65 21 49 -67 44 11 -64 52 16 51 0 0 -66 12 20 2 55 53 45 336 -3 -67 8 42 -65 16 52 -67 39 31 -64 47 16 52 0 0 -66 7 14 2 55 59 45 335 -2 -67 3 43 -65 11 40 -67 34 36 -64 42 0 53 0 0 -66 1 53 2 56 4 45 333 -2 -66 58 29 -65 6 11 -67 29 26 -64 36 28 54 0 0 -65 56 16 2 56 10 45 332 -1 -66 53 0 -65 0 27 -67 24 1 -64 30 40 55 0 0 -65 50 24 2 56 15 45 331 -1 -66 47 15 -64 54 28 -67 18 21 -64 24 36 56 0 0 -65 44 16 2 56 21 45 329 0 -66 41 15 -64 48 12 -67 12 26 -64 18 16 57 0 0 -65 37 52 2 56 27 44 328 0 -66 35 0 -64 41 39 -67 6 15 -64 11 40 Uncertainty in time = +/- 7 secs [Prediction of 2008 Mar 28.0] Data for the target star ------------------------ * name: 2UCAC 22751214 * constellation : Sagittarius * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 17 46 50.8223 DE: -22 52 12.939 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .037, .023 ) * V mag [mag]: 11.7 * B mag [mag]: 0.0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (20) Massalia approx. diameter [km]: 146 approx. diameter ["]: .090 distance from Earth [AU]: 2.23200 * orbital information: orbit source: Preston date of fit: 2008 Mar 27 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 1377 number of rejected observations: 252 time covered by the observations: 1900 Jul 17 - 2008 Feb 09 1 sigma uncertainty ellipse (major, minor, PA): 0.009, 0.007, 91° remarks: * orbital elements for (20) Massalia : Mean anomaly = 133.03699390 deg Arg. of pericenter = 255.60173890 deg Long. of node = 206.50187955 deg Inclination = 0.70683265 deg Eccentricity = 0.14246297 Semimajor axis = 2.40946994 AU Perihelion dist = 2.06620970 AU Mag: H = 6.45, G = 0.25 Epoch of elements : MJD 54557.12100000 TDT (2008 Apr 01.121) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 Apr 1 20 Massalia 2h 54.5m UT 11.7 17 46 50.822-22 52 12.942UCAC 22751214 0.0 11.3 146 17.4 2.232 1.342 0.41 33.2434 -22.871 137.35 4.65 2.9082 0.01568 -0.69257 4.71161 0.10431 -0.00555 0.00011 2000 131.1604332008 325.00000255.601739206.501880 0.7068330.14246297 2.4094699 2.0662097 6.5 5.00.25 RATE 2.6352490 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.038 0.024 90 1.27 0.024 0 54553.5020080401_751214 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 Mar 28, 06:15 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org