The Pamina and Ostena Asteroid Occultations of June 7, 2008

At the end of final exams week, this double asteroid occultation criss crossed through the Coalinga area early Saturday morning. David Dunham was in town, to set up several unmanned stations in addition to his own. Walt Morgan and other local observers also planned to set up stations for this. The Pamina path also crossed through the Phoenix and Tucson areas and so there were many observers lined up to get this one. Ostena was a tiny asteroid, only 22km, and the path precision was not great, but the star was bright - magnitude 6.5. This helped draw out the California asteroid occultationists. The Pamina event probability for our location was about 50/50, while Ostena was only 1 chance in 4. So part of the attraction for me was the extremely dark skies there and a couple of hours to do astrophotography first.

Chris Kitting (CSUEB marine biology professor and long time friend) joined me for this event, taking a day off from his mollusk conference in Monterey to help do some astro science. His goal was also to get some additional practice and testing done with his image intensified coupled with his telephoto lens and camcorder. A good thing, as it saved our Ostena event as it turned out. On the drive down, I stopped at the King City Taco Bell for dinner. Then to Hwy 198 and east to Parkfield Grade road, and a bit of scouting to insure a location that would have a good horizon for the 17 degree elevation Ostena occultation.

Chris, in safari gear. We're packing up my RAV4 at Cabrillo Observatory

Setting up our scopes in a creek bed in range land along Parkfield Grade road

Antares and the Rho Ophiuchi Complex. 8x10min stack with the 50mm Zuiko lens + UV/Haze filter, on ST2000XCM under clean skies. Color balanced more toward blue to take out reddening due to low altitude, along with the usual Photoshop and AstroTools favorites

Cabrillo's 10" LX200 w/ Meade f/3.3 focal reducer on alt-az mount, equipped with a PC 164c video camera and Kiwi II VTI and ZR 45MC camcorder recording device. The Pamina occultation target star was only 1 degree away from Jupiter, speeding identification of this faint 12th magnitude star.

The other people pix here were all taken with my Dimage A1. This one here was taken with Chris' Nikon D300. Much much improved (....but those D300's are very pricey!)

I had trouble locating the rising 10 Ceti target star for the Ostena Occulation and ended up watching the next closest star - Doh! Chris saved the day by recording the event using his telephoto lens and I3 image intensifier.

Chris' tape showed strong scintillation of the Ostena target star, but the star did not disappear during the10:49:48 predicted time or several sigma before or after. However, there was one perhaps unusually long disappearance at 10:50:10. In his words... "The apparent disappearance of that star was at 10:50:10 to 11 sec (closer to 11 sec, for ~1/2 sec), based on the WWV sound track. Individual video frames were too noisy to analyze frame by frame, alas. It is possible that the noise simply overwhelmed the star at that moment, causing the apparent (and subtle, brief) disappearance." After the event, I used bino's to help spotlight the star with the laser pointer so Chris could videorecord it and positively ID the star for later analysis. Then, we packed up at dawn and started the long drive home. I did stop once before we got on Hwy 101, for a 15 minute nod-off. Made it home w/o incident. An all-nighter!

Here is a sky-plane plot of all Pamina observations.