Observer: Richard Nolthenius
Asteroid, Star: (209) Dido, star= 2UCAC 17361090
Telescope: 8" Meade LX10 f/10, Alt-Az, 20mm eyepiece
Location: Karl Von Ahnen's front yard: 37° 05' 54"N,
121° 53' 23"W, elevation 1560 ft.
NAD83 coordinates from USGS map at topozone.com
Method: Voice/WWV/tape recorder
Sky: clear, fair seeing, star visibility: visible almost continuously with great difficulty, deteriorating as the event happened. Sun altitude at -11 and star altitude at 13 deg.
Timings: June 6, 2006 UT
begin: 11:38:00
D: missed, but event appeared to last a long time. Star D'd or lost around 11:39:20+- 5sec?
R: 11:39:42.4 +- 0.2sec
end: 11:40? deteriorating conditions make "end" a nebulous thing!
Comments: Didn't get the VTI working, with heavy tree cover and no satellite synch; I forgot the f/3.3 and couldn't locate and focus the star quickly enough on the screen. So pulled and went visual at the last minute. I lost the star probably because it disappeared; probability of an occultation at my location was 85% according to the predictions. Star only visible with averted vision, and it's visibility noticeably deteriorated during the 3 minutes or so of concentrated observing. "R" appeared definite and quick reaction time, perhaps because diffraction made it momentarily brighter. However, my first impression of the location of the "R" was a tad (less than 1 arcmin) north of the expected position, but this is uncertain as the tiny cresent of stars marking the reference was itself getting pretty hard to see in the lowering altitude and rising dawn. Derek Breit had an 8 sec occultation from well north of me, consistent with a slight south shift, and suggesting that I indeed should've gotten the full 16 second occultation predicted. His "R" was at 11:39:35.0, so adding 2.0 seconds for the delta in midtimes for our locations, and 4 seconds to account for my being on the centerline, gives a predicted "R" time for me of 11:39:41.0, so this seems consistent with my "R" being real.