This is a bright, long event that should permit a good search for moons and also shape determination. It's Alt=28, Az=207 barely east of the "teaspoon" formation in Sagittarius. It's at 8:49:21 pm and so is conveniently as the Comet A3 T-ATLAS is setting, but the tail may still be lurking above the horizon. There won't be time for optimum comet photography (my highest priority!) and the asteroid event too, so I will do both from the same site. Which site, is the question. The asteroid path does not go south of the Summit Area of Bonny Doon, it's possible perhaps to get a very short event at the southern limit at Andy's place on Summit. The centerline goes near the big parking lot area of Hwy 9 1.5 miles west of Saratoga Gap and a rather longer drive. It'll also require a bit of set up off the parking lot edge, to avoid trees that will hide the comet. How feasible and flat the ground will be to permit the photography is a question. I'm undecided which to try for. There's no ideal spots for both events that I can find.
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Clear skies at the big parking lot/view point on Hwy 9 1.5 miles west of Saratoga Gap. I chose this spot because it would have a good view of Comet A3 T-Atlas as well as be well inside the path for this asteroid occultation. I met Dave H from Astro 9 there, and we had a spectacular view of the comet, setting over distant redwood trees before the occultation. I ported the scope gear down from the parking lot (which was filled with hot rod'rs young people) along a path which allowed the comet to set closer to zero altitude, behind distant redwoods. I was perhaps 100 yards from the parking lot edge where the bathrooms are. While above any fog, it was still damp, but no clouds or fog appeared. No wind. I got on target without trouble, and decided 4x was needed. I used the dew shield. Afterwards, taking down the set up, I saw dew fogging the corrector plate. The scope spent about 35 minutes uncapped but dew shielded.
I used TME apertures. I had to cut out the time at, and before, when parking lot headlights turned on and aimed at our scopes 45 sec before the event. I used the period after the occultation as the metric interval, found the best moothing, which was rather short. Offsetting reference in time did not help flatness and left at 0. The occultation was essentially on predicted time but longer than the predicted duration; 1.44s vs. max duration predicted of only 1.1s. Perhaps irregular shape or reflectivity explains the larger chord. Kirk Bender also had a positive, from near Locatelli Meadow.
magDrop report: percentDrop: 74.6 magDrop: 1.490 +/- 0.338 (0.95 ci)
DNR: 3.08
D time: [03:49:19.6661]
D: 0.6800 containment intervals: {+/- 0.0254} seconds
D: 0.9500 containment intervals: {+/- 0.0709} seconds
D: 0.9973 containment intervals: {+/- 0.1708} seconds
R time: [03:49:21.1060]
R: 0.6800 containment intervals: {+/- 0.0254} seconds
R: 0.9500 containment intervals: {+/- 0.0709} seconds
R: 0.9973 containment intervals: {+/- 0.1708} seconds
Duration (R - D): 1.4399 seconds
Duration: 0.6800 containment intervals: {+/- 0.0388} seconds
Duration: 0.9500 containment intervals: {+/- 0.0914} seconds
Duration: 0.9973 containment intervals: {+/- 0.1927} seconds
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The Vizier lightcurve creation reads the gps from the IOTA report form, so I did pyote over. The D R timings are the same, but the containment intervals differ slightly.
Attached are the re-done pyote files together with the same pymovie files.
magDrop report: percentDrop: 81.2 magDrop: 1.814 +/- 0.543 (0.95 ci)
DNR: 3.47
D time: [03:49:19.9572]
D: 0.6800 containment intervals: {+/- 0.0192} seconds
D: 0.9500 containment intervals: {+/- 0.0497} seconds
D: 0.9973 containment intervals: {+/- 0.1290} seconds
R time: [03:49:20.8571]
R: 0.6800 containment intervals: {+/- 0.0192} seconds
R: 0.9500 containment intervals: {+/- 0.0497} seconds
R: 0.9973 containment intervals: {+/- 0.1290} seconds
Duration (R - D): 0.8999 seconds
Duration: 0.6800 containment intervals: {+/- 0.0291} seconds
Duration: 0.9500 containment intervals: {+/- 0.0665} seconds
Duration: 0.9973 containment intervals: {+/- 0.1424} seconds
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