The path for this goes across Santa Cruz and the Santa Cruz Mtns, and staying at home gives good coverage. The altitude is high, at 56 degrees, Az=282 due west. The duration is 2.9s and 2.6 magnitude drop. The rank is OK, Karl's odds of a hit are 86%, and it's 68% for my place. 92% on the centerline. The target is going down in the west so set up early it'll be higher than 56 degrees; it'll be 61 degrees up 20 minutes earler. This means you'll have to be wary of hitting the base with the gear. Shove the 8SE scope all the way up before doing 2-star alignment.
Predicted to drop 2.6 magnitude for up to 2.9seconds. But being blended with another star not much dimmer and just a few arcsec away, the actual observed drop will likely be closer to 1 mag.
The magnitude of the target is V=13.8 and brighter R=13.1. So W=13.4. For a duration up to 3sec, that should be quite do-able high in a dark, thin crescent moon 93 degrees away in the east.
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Both Kirk and I got positives on this one, although the target was blended with a close same mag neighbor that made analysis difficult.
My tape was difficult to reduce. The star on the video was much harder to see above background than it was on the LCD monitor. The blend with the other star similar in brightness to the target, was so close as to blend into a blurry combined image. In general, the stars on the video did not look as sharp as sometimes they do. Time stamps were not read somehow, too. So I have to do a manual time stamp entry in PyOTE. However, there were no dropped frames in the video, and the manual time stamps worked fine. The occultation itself is fairly clear compared to the other dips in the light during the taping. The reduction passed the 'false positive' test, but not by a great amount. Similar with Kirk's reductions, FP test was also passed but not by a lot. Our timings are consistent with each other, despite the noise.
I observed from home, at the base of the driveway.
My PyOTE reduction:
magDrop report: percentDrop: 61.7 magDrop: 1.041 +/- 0.407 (0.95 ci)
DNR: 2.08 setting=8x (4 blocks per integration)
begin= 10:58:24 UT, end=11:02:25 UT
D time: [11:00:03.1646]
D: 0.6800 containment intervals: {+/- 0.0729} seconds
D: 0.9500 containment intervals: {+/- 0.2740} seconds
D: 0.9973 containment intervals: {+/- 0.6676} seconds
R time: [11:00:04.4993]
R: 0.6800 containment intervals: {+/- 0.0729} seconds
R: 0.9500 containment intervals: {+/- 0.2740} seconds
R: 0.9973 containment intervals: {+/- 0.6676} seconds
Duration (R - D): 1.3347 seconds
Duration: 0.6800 containment intervals: {+/- 0.1206} seconds
Duration: 0.9500 containment intervals: {+/- 0.3439} seconds
Duration: 0.9973 containment intervals: {+/- 0.7444} seconds
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PyOTE reductions. I had to do manual time stamps. How to do this, look at the frame number beneath the PyMovie display of the video frame, and use the first (earliest) of the two time stamps as the associated manual time stamp, unless in field mode. I tried a few PyOTE reductions, but the best was using Ref1 as the reference star, and do a moderate smoothing of 38. At 8x, that's about a 10 second smoothing length. The FP test was passed, but not by a lot. Timings are consistent with Kirk's timings from his home across town.
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As of late on Oct 22, I've not yet filled out the IOTA report and sent it in.
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Karl got a recording from his front yard. Looks like a miss. He used 16x setting, which corresponds to 1/4s per integration. That would mean a max of 6 points for the occultation. Based on the predictions and the time difference between Karl and me/Kirk, Karl's mid point of occultation should have been at the 03.8 seconds after the minute mark. I've marked that on the light curves below. I note there was an obvious dip in Ref1 star just after that. But I confirmed that's truly Ref1 and not the target star, and no such dip is seen in the target nor in Ref2. I don't know how to interpret that dip, as it seems unlikely then to be a cloud. But regardless of which or how I smooth using ref1 or ref2, I don't see an occultation in Karl's light curve. I classify it as a miss, although I would have guessed that Karl would have had an occultation, based on the predicted 2.9 duration and the fact Kirk and I had 1.4 second events suggesting we really were closer to the southern limit, as predicted. Yet Karl was deeper into the predicted path on the north side.
Target light curve in PyMovie. I used a 4px circular aperture for all apertures. |
PyOTE light curve, after block integrating for 16x. |
I used a 222 frame Fourier Finder to generate this image and verify the target. |
I halted PyMOvie here, well after the known event, due to Ref2 getting too close to the top of the chip. |
Ref1, closest to the target, shows an anomalous drip about 2 seconds after the occultation should have occurred. Shorter dip seen in Ref2 an additional second or so after that seen in Ref1, and after the expected event. Passing cloud? |
PyOTE light curve using Ref2 as refernce star. Using the RN and KB light curves and using the offset in predicted time, the occultation center for Karl would be at 00:02.8 seconds after the hour mark. No dip in the target at that time. Nor when using Ref1 |
Summary on Karl's recording. A seemingly significant dip is seen in star Ref1, but it is not seen in the target except a smaller version 2 sec after the event would have occured. A dip also seen in Ref2 but later still. Possible drifting cirrus? When calibrating with reference stars ref1 or ref2, no dip seen in the target. When not using a ref star, still not dip seen at the time that would correspond to that seen by KB and RN in their events which passed the FP test and which occurred on time and depth. Most likely interpretation is a miss for Karl, even though a circular asteroid fit to Kirk and my observed occulation would imply Karl should have had a longer occultation of perhaps 2 seconds. It's a small asteroid; highly flattened? or did it shift so that Kirk and I actually were near the northern limit not the southern limit as most likely based on the rank?
