The Occultation of SAO 78252 by (146) Lucina

September 20, 2007

10:48 - 10:51 UT

Latest Update of this page:  September 19, 2007 07:53 AM (EDT - add 4 for UT)

Latest Cloud Cover Prediction

Latest News from David Dunham - 9 UT, Wednesday, September 19

The Astro Meteo 35h prognosis map, attached, that became available almost 3h ago is similar to the 46h prognosis 

described in my last message, but slightly worse, with a more varied and uncertain cloud pattern over northern 

California, and still very cloudy over most of the Dakotas and most of Minnesota.  If the 35h map is taken literally, 

the southern Sacramento Valley where many are planning to observe from sites near I-5 may be o.k. at the time of the 

occultation.  But for the northern 1/3rd of the path, that I want to try to cover, more cloudiness is expected in the 

northern Sacramento Valley with better conditions in that part of the path farther west along US 101 (but clouds are 

expected south of center along US 101).  Accuweather is forecasting worse conditions in northern Calif., with periods 

of rain along US 101.  Someone with a single small telescope who is mobile, able to change locations up to half an 

hour before the event, and then get on the target star, would have a good chance of finding a clear area within the 

path in northern California, especially if aided by someone looking at the IR weather satellite loop for the area.  

Tom Campbell said he would help me with that, so I suppose others might be able to call him at 813-621-6879 for advice 

for their mobile efforts as well.

Anyway, northern California is predicted to be very cloudy during the earlier part of the night; that and the
possibility of some rain makes it much harder to set up and run remote stations.  The weather forecast is much better, 

including during the several hours before the event, where the path crosses I-25/I-90 in northeastern Wyoming.  Seeing 

that, I bought a plane ticket from Denver to Sheridan, WY (the 930 mile round-trip distance is too far to drive), 

planning to change the Southwest ticket I already have from the Sacramento destination to Denver.  But then I tried to 

get a rental car in Sheridan, none were available!  I'm going to try Enterprise, but their office doesn't open until 

10 am EDT, so I won't be able to try to negotiate a vehicle with them until then.  Only if I can get a guarantee of a 

rental car from somewhere in Sheridan, will I change my flight from Sacramento to Denver.  I have changed my Sacramento 

flight to one that leaves at 3:35 pm EDT and arrives at 9 pm.  With that, I would probably have time to set up and run 

3 rather than 4 stations, especially if I use US 101 rather than I-5.  But this later departure will give me a chance to
get the next Astro Meteo weather update that should become available a little after noon EDT before deciding finally what 

to do.  If I can't get ground transportation in Sheridan, WY and if the weather prospects worsen in California, I might 

cancel all arrangements and save my Southwest funds for better opportunities in the future.

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- 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. 

_________________________________ 

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 prediction 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.

Overall View of Occultation

Star Field centered on Lucina with 1 degree field shown.

SAO 78297 is Mu (13) Geminorum, magnitude 2.9

     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 Hyades "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 
independent observation.  The event should be timed, even if only approximately, but do the best you can; 

timing methods are described here.

If an observation is tried, negative as well as positive results are important.  Download the 

Report Form template (Excel) at this link to report your Results.  Email addresses are on the Form.  

Here is an alternative Text Form that can also be used. 
_________________________________

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, since the medium-range weather forecast 
is very good for the Sacramento Valley, with clear skies (maybe a few cirrus moving in from the west, but the 

target is in the eastern sky).  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 77528 by 146 Lucina on 2007 Aug 21 Prediction by Steve Preston on July 8.2 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. 
                                                     
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 **
__________________ 

The station list below is unchanged from my last message, just changing Messner's site codes to W.  

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 M s. Fargo, ND Steve Messner mobile
 -68 58 M 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, 17h UT
cell phone 301-526-5590, e-mail dunham@starpower.net 
office e-mail david.dunham@jhuapl.edu (Blackberry)