This is another event only passing through Santa Cruz city, and then down to the south Monterey Bay. I'm on centerline. The target is in a rich Milky Way field, near open cluster NGC 6451. Alt=22, Az=176. I'll likely be the only one to attempt. Star is bright enough, but duration is only 0.3s so try for 2x.
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I got a recording. In the full light curve, at 4x, there's clearly a set of dropped numbers in the target centered very well on the predicted event time of 6:51:12UT. However, the sky was noisy and it only passes the FP test at the 3-sigma level. I used TME apertures on all stars. The very crowded Milky Way field may have also included dim but invisible stars w/o the TME tight apertures. The better ref star was ref2; brighter and a little less subject to noise. However, I actually ended up not using a reference star at all, as they did not seem to improve the signal on the target, and there was no evidence of cloud or drifting aerosol layers during observing nor in the light curves. The duration was 0.64s, which was twice the predicted 0.3s duration. The formal probability for my site for a 'hit' was 72%. Small asteroid, more likely to be oblong, but in any case the 2-sigma time error is 0.19s so the 0.3s duration is within 2-sigma error
Identifying the target star on the video was remarkably difficult. I spent a full half hour trying to ID stars and trace patterns on a 112 frame 'finder' and compare to the C2A LCD chart. So many stars were very different than their indicated sizes on the C2A chart. When I finally simply accepted that only most stars would be identifiable, it went faster and I found my way to the target. It was still quite faint, since the short 0.3s expected duration max meant I could go no more than 4x and get enough points to hope for it to show decently in the statistics. Fortunately, the occultation actually lasted longer, and was perfectly on schedule, and the reference stars and stability was good enough. Still, the event only passed at the 3-sigma level, but seems quite obvious on the light curves. Also, the sky level remarkably followed point by point to the target star and just barely dimmer, during the dip.
magDrop report: percentDrop: 78.1 magDrop: 1.651 +/- 1.541 (0.95 ci)
DNR: 2.66
D time: [06:51:11.9886]
D: 0.6800 containment intervals: {+/- 0.0495} seconds
D: 0.9500 containment intervals: {+/- 0.1902} seconds
D: 0.9973 containment intervals: {+/- 0.5047} seconds
R time: [06:51:12.6286]
R: 0.6800 containment intervals: {+/- 0.0495} seconds
R: 0.9500 containment intervals: {+/- 0.1902} seconds
R: 0.9973 containment intervals: {+/- 0.5047} seconds
Duration (R - D): 0.6400 seconds
Duration: 0.6800 containment intervals: {+/- 0.0871} seconds
Duration: 0.9500 containment intervals: {+/- 0.2716} seconds
Duration: 0.9973 containment intervals: {+/- 0.6157} seconds
Target star is not far about sky, but the TME aperture still was able to keep it comfortably significant above 'sky' |
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PyMovie shows the occultation rather well |
PyOTE raw light curve, showing the occultation |
Now adding the ref2 star and optimum smoothing and offset |
Zoomed in, showing the highly smoothed Ref2 star above, and the D and R confidence intervals in the solution. |
This light curve adds the 'sky' (no-star), and shows the depth of the event and noise follow the sky rather well. |
Neither Kirk nor Karl tried this one.
