100-km Asteroid (345) Tercidina Occ'n of 8.9-mag. SAO 145911, Nov. 14 pm, n. Calif. to n. Missouri
The star, near the water jug in Aquarius and only 10' from a 7.5-mag. star, was easy to find for those with working finders
The path shifted almost half a path-width north, so only the southern half of Tercidina was observed, from several stations in n. California and at least two in n.w. Nevada
Updated: 2005 Nov. 28
The last plan, as far as I know it (there were some last-minute trades), is below, along with results given so far. Code is c = probably clouded out, x = tried but failed to get an observation, + = positive observation with estimated duration of occultation, and - = negative observation (no occultation occurred). Blank means currently unknown/not yet reported. +100 *** 1-sigma s. shift southern limit *** +94 c Richard Dietz, Greeley, CO +74 x David Dunham remote #1 n. of Silver Springs, NV, prepointed wrong +64 *** predicted northern limit *** +60 c Harold Reitsema, mobile from Boulder, CO +54 + Cary Chleborad at Henry Grieb Obs., set up by Paul Maley, 7.9s +48 + David Dunham remote #2, Weeks, NV, about 8 seconds +41 Carson City, NV video fixed site +33 + Don Machholz, Colfax, CA, fixed, 7 seconds +27 + Paul Maley & Andrew Gallagher, Weimar, CA, 6.8 seconds +21 Charles Poplinger, Yorkville, CA +13 x David Dunham, Mason, NV, loose finder mount, star not found +6 + Walter Morgan mobile, Dunnigan, CA, 4 seconds +4 + Jim Stoffaire mobile, Smith Valley, NV, 4 seconds +1 + Sandy Bumgarner mobile, 3 seconds -15 Fred Schumacher mobile -20 - Richard Nugent mobile west of Sacramento, CA -24 - Glen Erickson, Davis, CA fixed, visual -28 - Derek Breit mobile, s. of Winters, CA -32 - Phil Sullivan, Occidental or Kenwood, CA -34 x Noel Lerner, Fiddletown, CA, star in tree 1 min. before -39 - Robert Innes, Sebastopol, CA -43 x Chuck Pullen, Wilton, CA, class late, not on target star in time -50 - Ed Morana mobile -60 - Red Sumner mobile -64 *** predicted southern limit *** -67 c Ron Lee, Falcon, CO -88 - John Westfall, Antioch, CA -95 x Robert Shelton, Walnut Creek, CA, equipment problems -100 *** 1-sigma s. shift southern limit *** -122 - Ron Bissinger, Pleasonton, CA -136 *** 2-sigma s. shift southern limit *** At least, I obtained a good recording of the occultation at +48 with a remote station. Accurate times are given at the bottom of this page, determined from the Kiwi time insertion; it's the first asteroidal occultation that I have timed with the Kiwi unit. At my attended site at +13, a loose mounting bracket for the finder prevented collimation so I wasn't able to get on the target star; that was very frustrating. Another lesson learned - never trust those things and bring the tools needed to tighten the bracket. For the remote at +74, I pointed the telescope using the finder to locate a single faint star in the video field of view; there were no other stars bright enough for more than 2 fields away, too far to trust. There were no other stars to confirm it, and there were no better opportunities during the next several minutes, and I wanted to leave to get to the attended site about 40 miles farther south. It turns out I pointed the telescope at a star a degree west of the one I intended, so the system did indeed record the target star, but unfortunately 4 minutes after the occultation. Another lesson learned - for pre-pointing, always confirm the field of view, preferably with an opportunity with at least two stars in a unique (within the area) alignment in the field of view that can be correlated with other stars nearby, at least in the finder scope. So I'm afraid this time we failed to get any observations of the northern half of Tercidina, since we had almost half a path-width north shift and there were no other observers north of the predicted northern limit, unlike the several fixed-site observers south of the predicted southern limit. Too bad there were no fixed-site observers in places like Chico, Redding, and Red Bluff, Calif. I think the errors in the positions of the TYC stars are larger than predicted since we are getting farther from the epoch of the Hipparcos satellite observations of those stars in 1991. The proper motions of the TYC stars had to be determined with the help of old ground-based observations, and I think those observations may have systematic errors that aren't taken into account in the determination of the errors of the proper motions. Maybe we should double the proper motion errors of the TYC stars to try to take this effect into account. The Hipparcos satellite determined the proper motions of the HIP stars, so predictions of those occultations continues to be good - note that the prediction for the occultation of Regulus by (166) Rhodope was very accurate, and so have most other predictions of occultations of HIP stars by low-numbered asteroids. Thanks for the efforts of all who tried to observe Monday night's Tercidina event; everyone's effort was valuable to get the coverage we obtained with the information we had before the occultation. The results show that even mobile observers aren't "guaranteed" to have an occultation; you need to keep trying, and about every other time, or every third time, you should succede. ___________________ 2005 November 15, occultation of 8.9-mag. TYC 5227-00241-1 = SAO 145911 by (345) Tercidina, 10cm SCT near Meeks, Nevada at WGS84 long. 119 deg. 14.3440' W., lat. +39 deg. 17.0543', h 1276m: U.T. 6:05:27 Star drifted into field of view, start of observation 6:06:33.30 +/-0.02s Disappearance 6:06:41.40 +/-0.02s Reappearance 6:08:00 Star drifted out of field of view, end observation ___________________ Extensive pre-event prediction information and plans can be found here. David Dunham