Occultation (Eclipse) of SAO 78252 by (146) Lucina on Sept. 20 - Updated 2007 Sept. 18, 22h UT
An occultation by a probable satellite of Lucina was observed in 1982
Observers in most of North America have a chance to confirm the satellite; observations are sought over a wide area
Please help us find the satellite, and if near the path, measure the size and shape of Lucina
This bright event is the best asteroidal occultation in North America during the rest of this year
Help us find (146) Lucina's satellite Thursday morning Sept. 20th! In April 1982, an occultation (eclipse of a star) by a probable satellite of (146) Lucina was video recorded with the 1-m telescope at Meudon Observatory near Paris, while the occultation by Lucina itself was observed in a different path crossing northern Spain. The observation implies an object at least 6 km across about 1600 km from Lucina, as reported in Icarus Vol. 61, pp. 224-231. Observers across most of the western and central USA, northern Mexico, and Canada west of Quebec have a chance to make confirmatory observations of the satellite if they monitor the easily-found 7.9- mag. star SAO 78252 only 2/3rds of a degree south of 3rd-mag mu Geminorum (Tejat). Especially those with video equipment in most of western North America are encouraged to record the star for a possible quick blink, expected to last about 0.3 second, that could be caused by the satellite (but if you don't have video equipment, such a "blink-out" should be easily noticed visually, so you are encouraged to look, with any small telescope or even good, steadily- held binoculars). In addition, observers in northern California, northern Nevada, southern Idaho, the northernmost part of Utah, northern Wyoming, s.e. Montana, n.w. South Dakota, s. & e. North Dakota, northern Minnesota, and western Ontario will have a spectacular occultation by Lucina that will last almost 7 seconds; visual, video, and CCD observers throughout those areas are especially encouraged to observe to help us determine the size and shape of Lucina. Lucina, a C-class ("carbonaceous") asteroid, is expected to be about 132 km across. _____________________ NEW INFORMATION BELOW __________________ AFTER ABOUT 0h UT Sept. 19 (Tues. evening 8 pm EDT) I will no longer be able to update this website. Brad Timerson will post later updates on his Web page for this event. Weather update Tues. 1 pm: Astro Meteo now has a forecast map, 47h prognosis, for 11h UT of Sept. 20, close to the time of the event. It shows clouds lingering over northeastern California, but clear in the northwest part. So those who were planning to drive up I-5 to intercept the path might have clearer skies if they drive up US101 instead. If this forecast is confirmed with the update that will become available shortly after midnight EDT tonight, I'll procede with my plans to fly to Sacramento, arriving there tomorrow about 2:30 pm. The update confirms that it will be overcast in most of N. Dakota and Minnesota; Steve Messner has little chance at his planned sites south of Fargo. The largest clear area over the path will be in western S. Dakota, north of Rapid City, and over n.e. Wyoming, a clearing behind a quickly-moving front. But just a few hours before, it will be cloudy there, so I am not very interested in trying it there myself since I wouldn't have time to pre-point my remote telescopes before the event. Skies will be partly cloudy from s. Idaho to central Wyoming, so observers will have a reasonably good chance to see the event there, although it's not guaranteed. _________________________________ The rest of this message has the following sections: 1. Information about the Sept. 20th occultation by Lucina. 2. How to observe and confirm an occultation by Lucina's satellite. 3. Station list for the Sept. 20th occultation by Lucina _________________________________ 1. Please help us Wednesday night, actually early Thursday morning, Sept. 20, at 10:48-10:50 UT (3:48 am PDT, 4:49 am MDT, 5:50 am CDT, and 6:50 am EDT), to measure the size and shape of the approximately 132-km asteroid (146) Lucina by observing and at least approximately timing its occultation of 7.9-mag. SAO 78252 (= TYC 1327-00069-1) 2/3rds of a deg. south and a little west of the 3rd-mag. star mu Geminorum (Tejat); the target star is actually in Orion's club a little south of the border with Gemini. The path was described above. On or very close to the central line are Ukiah and Chico, CA; Winnemucca, NV; Pocatello, ID; between Buffalo and Sheridan, WY; Valley City & 25 mi. n. of Fargo, ND; Bemidji, MN; and Quetico Provincial Park, ON. On or near the predicted northern limit Red Bluff; about 15 mi. n. of Idaho Falls; Powell, WY; just north of Bismarck and over Grand Forks, ND; over Thief River Falls and just north of International Falls, MN; and over Lake Nipigon, ON. On or near the predicted southern limit are Santa Rosa, Yuba City, and Truckee, CA; Reno, Battle Mtn., and Elko, NV; Gillette, WY; Spearfish, SD; Hibbing, MN; the MN/ON border at the shore of Lake Superior; and Kapuskasing, ON. Of course, as noted above and in item 2 below, an occultation by a satellite of Lucina, possibly the one that caused the 1982 event or another one, is possible from a much wider zone, from which observers are encouraged to monitor the star as well. If an occultation occurs, there will be an easily-seen, even spectacular, 6-mag. drop (to the 14th mag. of Lucina) predicted to last 6.8 seconds for a central event. The first-quarter Moon will be below the horizon for all observers. In Ontario, the event will occur in brightening dawn twilight with the sunrise point in western Quebec. In any case, please let me know if you might try to observe this occultation from at or near home, or if you might be mobile, so we can effectively target mobile observers to avoid duplication of observations by fixed-site observers. I'll update the long station list below to show plans with a future message after receiving responses from potential observers. Even better, I recommend installing new software called Occult Watcher, where you input your position and it searches Steve Preston's predition Web site, informing you of all asteroidal occultations in your region during the next 4-5 weeks, giving probabilities and other details. Whenever a path is updated, the software lets you know. It also has provision for you to specify your observing intentions, and these are displayed along with those of other observers to help plan the overall coverage for the event. Hristo Pavlov in Sydney, Australia wrote this program; you can get it here. FINDING THE TARGET STAR The star is in a rich part of the northern Milky Way at J2000 RA 6h 20m 32.1s, Dec +21 deg. 05' 27", 2/3rd deg. south- southwest of 3rd-mag. mu Geminorum (Tejat) which, with the similar red-giant star eta Geminorum (Propus) make a distinctive pair a degree apart in the western corner of the Gemini "rectangle". The target star is the westernmost of a small (0.2 deg. long) distinctive asterism (kind of a broken line) of 4 8th-mag. stars that should be very easy to recognize in finder scopes or even good binoculars. Path maps and detailed finder charts of different scales are on Steve Preston's Web page for the event here. Additional useful information is on Derek Breit's Web site - scroll down to the line for this event on UT Sept. 20 at 10:51 UT, then click on "GoogleMap" for the interactive Google map of the path that you can zoom in on it to great detail. If you double-click inside the map on the place where you want to observe, the coordinates and distance from center of the location will appear at the bottom of the map (with + for north and - for south). Click on "Sites" for a long list of stations sorted by distance from the central line, giving the predicted time of the occultation at the site, and the Sun & star altitudes at the time, and the probability for an occultation there (if your site is not in the list, either you are not within 3-sigma of having an occultation, or you may not be in the master list - to check the latter, contact Derek Breit at breit_ideas@hotmail.com). The list uses accurate coordinates provided to us for the calculations, but the list only displays the coordinates to the nearest 5' for privacy concerns. A shortened version of the list is below. Let me know if your station is not on the list; if you can provide coordinates or a postal address, we can add your location. Clicking on "stars" gives a list of stars that can be used to pre- point a stationary telescope to the direction of the occultation star before the event, useful mainly by those trying to run remote stations. In this case, I think that it is easier to find the target star directly than to try the pre-pointing technique, but there is a good pre-pointing opportunity. Mars is the brightest object in that part of the sky (but don't confuse it with the bright orange star Aldebaran, part of the Haydes "V" pattern about 15 deg. west of Mars); 3rd-mag. zeta Tauri will be the only relatively bright star close to Mars (2 deg. southwest of it). If you center your telescope on zeta Tauri (J2000 RA 5h 37.6m, Dec 21 deg. 9') and turn off your clock drive, clamping the telescope so it won't move, the target star will appear 4' south of where zeta was 42m and 46s later. _________________________________ 2. As noted above, those well away from the path are encouraged to watch for a possible occultation by a possible satellite. The 1982 event was 1600 km from Lucina, about 12 Lucina diameters. This means that all observers should monitor the star for at least 1.5 minutes before to 1.5 minutes after the time of closest approach for their location. Since the shadow sweeps across the dark part of North America in less than 3 minutes, all observers can use 10:47 to 10:52 as the observing window; watching another minute earlier (especially in the West) and/or later (especially in the East) won't hurt. Lucina's motion relative to the Earth is fast, 19 km/sec., so an occultation by the possible object that caused the 1982 event at Meudon will be only 0.3 second. That could be noticed visually (but try not to blink!), but a video recording is better to document the event. Visual observers should try to arrange to observe in pairs. That is, try to get a friend to observe from another location nearby, but preferably at least 100 meters away to give a more indepenent observation. The event should be timed, even if only approximately, but do the best you can; timing methods are described here. _________________________________ 3. Below is a partial list of stations, similar to station lists that I've distributed for previous events. At the end of the list, I include a shortened version of it including just those who have said that they plan to observe this occultation. So far, most of the observers are mobile; we need to get a better idea of who might be trying to observe the occultation from fixed sites in and near the path. Especially, observers in the Sacramento region, and north of San Francisco, are sought. In any case, claim your "chord" (distance from the central line) now so that mobile observers can avoid your line. In the list below, "north" or positive distances from center are more to the northwest, of center, while "south" or negative distances are more to the southeast, of center. Occultation of SAO 78252 by 146 Lucina on 2007 Sep 20 Prediction by Steve Preston on Aug. 13.1. The 2nd column gives the probability that an occultation will occur at the location. You need to use a fixed-space font such as Courier for the table to display properly. All observers especially within the "2-sigma" limits are encouraged to observe, at least from convenient near-home locations, and of course much farther away for checking for satellites. NOTE THAT THIS IS ONLY A LIST OF POTENTIAL OBSERVERS AND POSSIBLE OBSERVING STATIONS; I'M SURE THAT NO OBSERVATION WILL BE MADE FROM MOST OF THESE LOCATIONS, SO ANY OBSERVATION THAT YOU CAN MAKE WILL BE VALUABLE. See the updated shorter list at the bottom for observers who say they are planning to try the event. Occultation of SAO 78252 (TYC 1327-00069-1 by (146) Lucina on 2007 Sep 20 P r Dist. o U.T. from b 10h Star Sun center. Location, observer and Alt Alt km % m s o o 212 0 ** Northern limit plus 3-Sigma ** 198 0 Boise ID 48 55 43 -28 195 0 Eureka CA 48 26 37 -35 173 2 Billings MT 49 24 48 -22 167 2 ** Northern limit plus 2-Sigma ** 124 15 SurpriseVlyHotSpg, CA 48 38 40 -32 122 16 ** Northern limit plus 1-Sigma ** 110 23 Redding CA Schreder Pln. Adams 48 29 39 -34 96 33 REGAN ND LEPPERT~JOHN 49 52 52 -17 81 46 GRAND FORKS ND GAFFEY~MICHAEL 50 5 53 -14 81 46 730 University of North Dakota 50 5 53 -14 77 50 *** Northern limit *** 76 50 E E Barnard Obs Allan Morton 49 8 46 -25 61 63 Bismarck ND 49 50 52 -17 31 83 MENDOCINO CA POPLINGER~CHARL 48 22 38 -35 28 85 Sheridan WY 49 25 49 -22 1 91 Pocatello ID 49 3 46 -26 0 91 **** Centre Line **** -35 81 Fargo ND 50 3 54 -14 -39 79 Gualala CA 2001_9 7RobertInnes 48 20 38 -36 -54 69 Thunder Bay ON Randy McAllister 50 31 57 -9 -68 57 Armstrng CA Nolthenius mobile 48 21 38 -36 -71 55 NevadaCy CA Wayne Watson 48 28 40 -34 -77 50 *** Southern limit *** -78 49 Dunnigan, CA 48 24 39 -35 -80 47 G64 Blue Canyon Observatory 48 29 40 -34 -80 47 SAN RAFA CA HUME OBSERVATORY 48 21 38 -35 -82 45 Grass Valley CA Dunckel~Peter B 48 27 40 -34 -86 41 Occidental CA Phil Sullivan 48 20 38 -36 -87 41 Reno NV Arthur Johnson 48 32 41 -33 -92 37 SANTA ROSA CA LOYER~GEORGE E. 48 21 38 -35 -92 36 Colfax CA Don Machholz 48 27 40 -34 -96 33 Sebastopol, CA Robert Innes 48 20 38 -36 -100 30 Kenwood, CA FergusonObs.,8 48 21 39 -35 -104 27 PENNGROVE CA BUMGARNER~SANDY 48 21 39 -35 -111 23 Winters CA 48 23 39 -35 -112 22 Rocklin CA SierraCol.DaveKenyon 48 26 40 -34 -118 18 DAVIS CA ERICKSON~PROF. 48 24 39 -35 -121 16 Pt Reyes - Vision 48 19 38 -36 -122 16 Dayton, NV Red Sumner 20cm 48 31 41 -33 -122 16 ** Southern limit plus 1-Sigma ** -122 16 Carson City, NV -J Davis OBS 16" 48 30 41 -33 -124 15 G66 Lake Forest Observatory 48 26 40 -34 -125 14 Dayton CA Red Sumner 48 31 41 -33 -125 14 Carson City NV 48 30 41 -33 -126 14 Sacrmnto CA Manuel Tsihlas 48 24 39 -35 -126 14 Sacramento CA Lerner~Noel 48 25 39 -34 -131 11 CameronP CA Charlie Coburn 48 26 40 -34 -139 9 Sacramen CA Jim Varney, S.V.A.S 48 24 39 -35 -141 8 726 Brainerd 50 10 56 -13 -150 5 Duluth, MN Bob King 50 19 57 -11 -151 5 WILTON CA PULLEN~CHUCK 48 24 40 -35 -154 4 Duluth MN Douglas Dunham 50 19 57 -11 -155 4 RapidCity SD 49 34 52 -20 -156 4 MARTINEZ CA Breit~Derek 48 21 39 -35 -157 4 Fiddletown CA 48 26 40 -34 -158 4 Duluth MN 50 19 57 -11 -163 3 455 CBA Concord 48 21 39 -35 -164 3 Superior WI 50 19 57 -11 -165 2 BERKELEY CA FREEMAN~TONY 48 20 39 -35 -166 2 Berkeley CA Schrier~Joshua 48 20 39 -35 -166 2 660 Leuschner Observatory, Berk 48 20 39 -35 -167 2 ** Southern limit plus 2-Sigma ** -169 2 WlnutCrk CA Tom Case (&Rowley) 48 21 39 -35 -170 2 SanFrancisco CA 48 19 39 -36 -173 2 SAN FRAN CA William Westbrooke 48 19 39 -36 -173 2 Walnut Creek CA Shelton~Robert 48 21 39 -35 -174 2 Fremont CA D. Anderson 48 20 39 -36 -174 2 ANTIOCH CA WESTFALL~JOHN E 48 21 39 -35 -175 1 Oakland CA Chabot Obs. (new) 48 20 39 -35 -178 1 SAN LEANDRO CA GINGRICH~MARK 48 20 39 -35 -183 1 Ogden UT 48 58 46 -27 -183 1 Brisbane CA 48 19 39 -36 -187 1 Fred Schumacher 48 27 41 -34 -188 1 Ogden UT J. R. McCormick 48 58 46 -27 -189 1 Castro Valley CA Skelly~Bruce J. 48 20 39 -35 -191 1 CastroVl CA Bob Sills 48 20 39 -35 -192 1 Stockton CA Jeff Baldwin 48 23 40 -35 -194 0 Uinta UT Keith Finlayson 48 58 46 -27 -196 0 918 Badlands Observatory, Quinn 49 37 52 -19 -199 0 PLEASANTON CA MORGAN~WALTER V 48 20 39 -35 -201 0 BELMONT CA HART~JIM 48 19 39 -36 -202 0 LIVERMORE CA MORANA~ED 48 21 39 -35 -202 0 HALF MOON BAY CA FRANK~CHRISTOPH 48 18 39 -36 -202 0 Livermore Carlos Avalle 48 21 39 -35 -204 0 G61 Pleasanton 48 20 39 -35 -204 0 UNION CITY CA GARFINKLE~ROBER 48 19 39 -36 -205 0 Livermor CA Jim Ferreira 48 20 39 -35 -206 0 Pierre SD 49 44 53 -18 -212 0 Manteca CA Fred Schumacher 48 22 40 -35 -212 0 ** Southern limit plus 3-Sigma ** _______________________________________ Short updated list of committed observers Below, codes between the "Probability (Prob.)" column and the location, observer is * for visual observers, V for video, m for mobile visual, and M for mobile video. w is for a visual observer likely to be clouded out while W is similar for a video observers. I have taken most of the observer information below from the Occult Watcher list. As noted above, I'll probably shift my sites to US 101, and others now planning on I-5 may also do that. Occultation of SAO 78252 (TYC 1327-00069-1) by (146) Lucina on 2007 Sep 20 P r Dist. o U.T. from b 10h Star Sun center. Location, observer and Alt Alt km % m s o o 537 0 V Umatilla, OR Tony George sat. search 212 0 ** Northern limit plus 3-Sigma ** 167 2 ** Northern limit plus 2-Sigma ** 122 16 ** Northern limit plus 1-Sigma ** 88 39 M Cottonwood, CA D. Dunham mobile 77 50 *** Northern limit *** 68 57 M n. Red Bluff, CA D. Dunham N.remote 46 74 M Hwy A11, w. Tehama, CA D. Dunham cen.remote 25 85 M Walter Morgan remote 24 86 M Walter Morgan mobile 15 89 M IOTA West mobile observer 9 90 M Navarro, CA Charles Poplinger 0 91 **** Centre Line **** -2 90 M Paul Maley mobile -15 89 M IOTA West mobile observer (R. Nugent?) -26 85 M Derek Breit remote -28 84 M Derek Breit mobile -47 73 M s. Williams, CA D. Dunham S.remote48 26 39 -35 -56 67 W s. Fargo, ND Steve Messner mobile -68 58 W s. Fargo, ND Steve Messner remote -68 58 M Armstrong, CA R. Nolthenius -77 50 *** Southern limit *** -82 45 V e. Windsor, CA HUME OBSERVATORY 48 21 38 -35 -122 16 ** Southern limit plus 1-Sigma ** __________________ David Dunham, 2007 Sept. 18, 22h UT cell phone 301-526-5590, e-mail dunham@starpower.net office e-mail david.dunham@jhuapl.edu (Blackberry)