Good Occultation by (602) Marianna Sun. am, March 12
Detailed maps of the path can now be produced from Charlie Ridgway's interactive Web site with new link given below
This occultation of a star visible in most finder scopes and binoculars may be the best in the USA this winter
Updated: 2006 March 11
We need your help to measure the size and shape of the approximately 125-km C-class outer main-belt asteroid 602 Marianna by timing its occultation of 7.8-mag. SAO 210276 (HIP 90871) on Sunday morning, March 12, an hour or two before sunrise (fpr all observers, the occultation is expected to occur at 11:56 UT = 5:56 am CST or 4:56 am MST) in a path that will cross southwestern Colorado (possibly as far north as Denver), northeastern New Mexico (possibly as far south as Santa Fe), and northwestern and central Texas. The path extends eastward over Houston, but twilight will be rather bright there with the star in the southeast, making observation there difficult, but maybe not impossible. The star is bright enough that it might be seen with a steadily mounted (held firmly against a fence post or other stable object) pair of binoculars, but a small telescope is recommended if you have one. Use whatever means you have to time the event, with simple methods explained here. We will try to coordinate coverage of the observation; please let me know if you will attempt an observation so that mobile observers can be directed to locations to avoid your line across the asteroid. THE PATH The path, which projects to an estimated 213 km wide, is shown on my map on p. 61 of the March issue of Sky and Telescope, but it's better to see the latest updated path on Steve Preston's Web site. Although the new path is almost the same as the one in S&T, Preston's map also shows the 1-sigma limits as dashed lines where it's very possible that the occultation could occur, at locations such as San Antonio and Fort Worth; observers within those dashed lines, and a little outside of them (since a path shift greater than 1 sigma is very possible) are also encouraged to try to observe the occultation. The 1-sigma path error is 0.36 path-widths. Very detailed views of the path are at Charlie Ridgway's interactive maps Web site. It has an offset line that you can specify to either iteratively figure out the distance of a given location from the predicted central line in km, or for mobile observers, to find sites at a specified distance from the central line. That site doesn't specify the time, but that can be found from the maps and data on Preston's Web site; the time for a given location estimated from his site should be accurate to about a tenth of a minute. THE STAR AND THE OCCULTATION The spectral type B9 star is at J2000 R.A. 18h 32m 13.4s, Dec. -37 deg. 12' 45", in Corona Australis near the Sagittarius border just over 3 deg. south-southeast of the bright star Kaus Australis (epsilon Sagittarii) at the bottom of the teapot's spout. The target star is about 1.5 deg. north of 5th-mag. kappa Coronae Australi and 0.4 deg. south-southeast of a 7th-mag. star; other 8th- mag. stars in the area should make it not too difficult to find the target, but as usual, allow plenty of time to find it. Detailed finder charts can be found on Steve Preston's Web site but I have trouble now printing those maps directly from my Web browser; only a small part of them print. So I have put them in this Power Point file that allows you to view and print the whole charts. If an occultation occurs, there will be a 6.7-mag. drop to the 14.5-mag. of the asteroid (which won't be visible except in large telescopes) lasting 5 seconds for a central event. The observations might reveal the star to be a close double, in which case, the disappearance and/or reappearance will occur in steps. The 94% sunlit waxing Moon will setting, or very low in the west, in the opposite direction from the target star, so it is not likely to be as much of a factor for finding the star than the relatively low altitude above the horizon and, for those in eastern Texas, the brightening dawn twilight. WEATHER The first Astro Meteo (Clear Sky Clock) forecast shows mostly clear skies across Texas, but with a wedge of clouds extending from the south to San Antonio and Austin (but fortunately clear not very far north of there). It even shows clear in Houston, but twilight may still be a problem there. Some thin clouds are shown around Ft. Worth. Patchy clouds are expected over most of New Mexico and Colorado, but clear in the eastern third of N.Mex. and the s.e. corner of Colo., so although generally not good, observers there have some chance. You can see the Astro Meteo cloudcover forecast maps in this Word file. Another update will be available soon. STATION LIST AND COORDINATION OF COVERAGE A list of dozens of cities and stations within 3 sigma of the path is at Derek Breit's Web site. From his station list, arranged by distance from the predicted central line, you can see the predicted time of the occultation for your location, as well as the altitudes of the star and Sun, and the probability for an occultation by Marianna. Below is an edited version of that list, removing most stations and indicating those who have said they will try with a notation in the column between the distance and the probability, with f = fixed-site observer, m = mobile observer, and w = fixed-site observer likely to be clouded out. Blank means that the observer has not responded, but I hope that they might try and let me know; in the meantime, mobile observers might locate near their chord, but not directly on it; I'll eliminate most of these in my next lists (also included are a few cities without known observers). We have two locations for Mitch Brumbelow and Ed Vinson in/near Snyder, TX; I'm not sure which location is the home location. I'll make another update of this about 11 am EST Sat. Mar. 11 before I leave home. I plan to meet Rick Frankenberger in San Antonio, e-mail rickf@stic.net and will try to distribute a final list from there about 9 pm CST Saturday evening. In the list below, I've made a preliminary selection of distances for mobile observers, but these can be changed later to give a better distribution as more fixed-site observers might become known, or to more realistically reflect what they can do. The list below is actually my 2nd update since a few more observers have sent me their plans, and the weather forecast has changed, a little better than the earlier Accuweather forecasts. Note that you need to display the list with a fixed- space font such as Currier for the columns to line up properly, and you will probably need to change to a smaller font size to prevent line wrapping. Occultation of SAO 210276 = HIP 90871 by 602 Marianna on 2006 Mar 12 Distance from center of occultation path - in km Proba- Location LongitudeLatitude alt U.T. Alt Sun km bility o ' o ' m h m o o 334 0% ** Northern limit plus 3-sigma ** 259 2% GREELEY CO DIETZ~RICHARD D-104 42.3 40 24.3 1459 11 56.7 7 -16 258 2% ** Northern limit plus 2-sigma ** 238 4% Dallas TX John L. Cotton - 96 47.7 32 51.1 174 11 57.0 16 -10 238 4% Canadian TX Terrill Bartlett -100 22.9 35 53.9 800 11 56.8 12 -13 225 6% Trophy Club TX W Barry Smith - 97 11.0 32 59.9 200 11 56.9 16 -10 218 7% Longmont CO Steve Albers -105 6.6 40 10.8 1524 11 56.7 7 -16 212 8% WichitaFalls TX - 98 29.5 33 54.6 288 11 56.9 15 -12 207 9% Arlington, TX Robert Brown - 97 7.3 32 42.6 0 11 56.9 16 -10 205 10% Denver CO Moravec~Jim -105 0.0 39 51.0 1609 11 56.7 7 -16 201 11% Arlington, TX Russell Johnso - 97 8.5 32 38.8 0 11 56.9 16 -10 198 11% DENVER CO DENVER MUSEUM O-104 59.0 39 44.0 1615 11 56.7 7 -16 197 12% Boulder CO Som-BashOb. Durda -105 15.8 40 0.2 1653 11 56.7 7 -16 197 12% Fort Worth TX - 97 19.7 32 44.9 204 11 56.9 16 -11 183 16% Elbert CO ScottDonnellKiowaCk -104 34.7 39 4.3 2230 11 56.7 8 -16 183 16% Benbrook, TX Ron DiIulio - 97 27.4 32 40.2 0 11 56.9 16 -11 182 w 16% MtThrodn CO Richard Keen -105 23.5 39 52.6 2727 11 56.7 7 -16 182 16% ** Northern limit plus 1-sigma ** 182 16% LITTLETON CO OLASON~MICHAEL -105 6.0 39 36.0 1896 11 56.7 7 -16 183 w 16% Elbert CO ScottDonnellKiowaCk -104 34.7 39 4.3 2230 11 56.7 8 -16 181 16% GRAND PRAIRIE TX FLEMING~TOM - 97 30.0 32 40.8 169 11 56.9 16 -11 174 19% FALCON CO LEE~RONALD G. -104 33.7 38 56.9 632 11 56.7 8 -16 173 19% ColoradoSprngsCO WARNER~BRIAN D.-104 45.0 39 05.6 2316 11 56.7 8 -16 151 28% ColoradoSpgs CO -104 49.3 38 50.1 1821 11 56.7 8 -16 126 40% Pueblo CO -104 36.6 38 16.3 1428 11 56.7 9 -16 124 w 40% Steamboat Springs CO J Westlake -106 49.9 40 29.1 2050 11 56.6 6 -17 116 45% Waco TX - 97 8.0 31 33.2 123 11 56.9 17 -11 112 47% Miners View, CO Trina Ruhland -106 3.7 39 28.0 3350 11 56.6 7 -17 111 48% WACO TX MCANALLY~JOHN W- 97 12.0 31 32.5 184 11 56.9 17 -11 109 f 49% Houston TX Dave Clark - 95 11.3 29 59.5 0 11 57.0 19 -9 107 49% LORENA TX BARTON~JOHNNY - 97 5.0 31 24.3 309 11 56.9 17 -10 107 50% *** Northern limit *** 105 f 50% Stephenville TX HUDGENS~BEN - 98 7.4 32 12.2 415 11 56.9 16 -11 102 52% Baytown, TX Steve Linscott - 94 56.9 29 43.7 0 11 57.0 20 -9 101 53% Stephenv TX Douglas Mayo, 8"C - 98 13.0 32 13.2 414 11 56.9 16 -11 87 m 56% Richard Nugent mobile 94 56% Amarillo TX -101 50.1 35 12.5 1122 11 56.7 12 -14 78 f 64% Houston TX Cudnik~Brian - 95 36.4 29 56.0 40 11 57.0 19 -9 60 m 65% David Dunham mobile 40 m 80% David Dunham remote 21 m 82% Abilene TX P.Maley +8 to +30 km - 99 43.9 32 27.1 521 11 56.8 16 -13 2 m 84% s Ralls TX Tom Heisey 2 -101 24.0 33 37.0 1000 11 56.7 14 -14 0 84% **** Centre Line -12 m 83% Paul Sventek mobile 11 56.9 19 -10 -24 w 82% Austin, TX MikeMcCants8in - 97 45.7 30 20.0 158 11 56.9 18 -11 -25 82% s Caldwell TX Tom Heisey 1 NO -101 57.5 33 44.9 1015 11 56.7 14 -14 -33 m 80% Hal Povenmire mobile with DWD system -37 79% Snyder TX Brumbelow~Mitch-100 54.2 32 41.9 718 11 56.7 15 -14 -38 79% SNYDER TX VINSON~EDWARD -100 55.0 32 42.3 369 11 56.7 15 -14 -38 79% LUBBOCK, TEXAS -101 53.6 33 32.2 0 11 56.7 14 -14 -39 79% Snyder, TX Mitch Brumbel -100 55.9 32 42.0 718 11 56.7 15 -14 -47 m 77% Eric Juhre mobile from San Antonio -50 75% Dunn, TX Ed Vinson, 7. -100 55.2 32 32.8 674 11 56.7 15 -14 -69 68% CLOVIS NM KRAJCI~TOM -103 19.9 34 23.9 0 11 56.6 12 -16 -61 m 67% Johnson City TX Jack Peterson 0 11 56.8 18 -12 -65 65% Frankenberger lot (sorry, too close to Peterson's site) -82 m 60% Rick Frankenberger mobile -104 51% VICTORIA TX STOCKBAUER~DON - 97 1.9 28 50.5 27 11 56.9 20 -11 -106 50% San Angelo TX -100 26.1 31 27.7 562 11 56.7 16 -13 -107 50% *** Southern limit *** -130 38% SAN ANTONIO TX SLATER~DAVID - 98 39.0 29 45.7 402 11 56.8 18 -12 -136 m 35% nwKerrville TX Pete Noland - 99 18.2 30 11.8 710 11 56.8 19 -12 -148 29% EagleCk. TX Kevin Muenzler - 98 14.8 29 14.9 0 11 56.8 19 -12 -153 w 27% SANTA FE NM MROZ~GENE -106 0.8 35 42.6 2097 11 56.5 10 -18 -153 27% SanAnton TX Daniel Ramirez III - 98 40.6 29 31.3 0 11 56.8 19 -12 -159 24% WhiteRck NM David Palmer -106 12.7 35 49.1 1889 11 56.5 10 -18 -177 18% Midland, TX Craig Smith,C8 -102 9.8 32 2.5 0 11 56.7 15 -15 -182 16% ** Southern limit plus 1-sigma ** -230 5% Albuquerque, NM Bruce Levin ne -106 31.0 35 11.0 1774 11 56.5 11 -18 -237 4% ALBUQUERQUE NM DULLECK~GEORGE -106 29.3 35 5.6 0 11 56.5 11 -18 -246 3% SALT LAKE CITYUT WIGGINS~PATRICK-112 17.7 40 38.5 1311 11 56.4 4 -21 -258 2% ** Southern limit plus 2-sigma ** Let me know if you might be mobile for this occultation, and/or if you might be able to help with my planned effort to observe it from three separate locations north of San Antonio, where I'll be arriving early Saturday evening. __________________________________________________ David Dunham, IOTA home dunham@starpower.net 301-474-4722 cell 301-526-5590 office david.dunham@jhuapl.edu 240-228-5609