The OWc map, when clicked on my Scotts Valley position, says event time is 1:55:48am, not :49.
This path goes through Scotts Valley and over Karl's place. 31 degrees altitude, Az=174, in eastern Sagittarius. Duration 0.4s and full drop of 5 magnitudes. Weather looks good. I was originally quite skeptical this would be do-able, but Karl was game for it, as it was a high rank event and he was on the centerline. So, I went for it too, and so did Kirk.
The RUWE = 1.05, which is good, and within the RUWE limit of 1.2 for being good. Star position seems solid.
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The OWc map, when clicked on my Scotts Valley position, says event time is 1:55:48am, not :49. |
Here's the layout of our actual observed sites. I was dead on the centerline. Karl north of me, Kirk south of me. I had a 2 integration drop to zero (sky level). However, it is 4s after the predicted event time. Clearly from Kirk's miss, the tight confidence limits on the path are clearly wrong and something bad happened in the orbit calculation. So, a guess as to how far off the actual orbit and position was, is unknown.
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I obesrved this from a new spot that's good for future events and quick to get to. Off Santa Claus Lane to Polo Road, there's distant parking spaces w/ no lights looking east and south across a large empty field. It is separated from the freeway Hwy 17 by trees. I got a good recording at 4x. The target was easier to see than I anticipated. Was tempted to do 2x, but given the partial occultation expected, I went back to 4x.
1st Analysis: TME apertures on all stars
There are two adjacent points 3 sec after the predicted time, that are both at effective zero (sky values), they are the only two consecutive such points, and they are the two lowest points in the entire light curve. I had to use the event duration method to find a solution. Detectable at 2 integrations and 4.8 mag drop, which is what I observed. PyOTE does find and calculate a solution, but the red bar is at 2-sigma, signifying only a 95% odds it was real. The problem is that the time is 4 seconds after the predicted time. Now, I was on the centerline and it was a high-rank event. I would have clearly seen a 0.4s event if it happened. The target star was easily significant on all frames except this pair shown. So, the orbit was clearly off. By ~10 diameters?? Kirk's observation is clearly most consistent with a "miss", and it would be hard to draw an asteroid that would fit a very short event for both Kirk and I and be anything close to round. If Karl's observation is a convincing miss or very near miss, then my 0.15s event would be wrong. Either Kirk or Karl would have had to have had a much longer event of duration 0.3 or so seconds. Kirk clearly did not. Did Karl? His visual impression was "no", but I need to see his PyMovie results to be sure.
Nov 9 2024 analysis
magDrop report: percentDrop: 94.4 magDrop: 3.123 too much noise; cannot calculate error bars
DNR: 3.89
D time: [08:55:51.9067]
D: 0.6800 containment intervals: {+/- 0.0241} seconds
D: 0.9500 containment intervals: {+/- 0.0622} seconds
D: 0.9973 containment intervals: {+/- 0.1666} seconds
R time: [08:55:52.0666]
R: 0.6800 containment intervals: {+/- 0.0241} seconds
R: 0.9500 containment intervals: {+/- 0.0622} seconds
R: 0.9973 containment intervals: {+/- 0.1666} seconds
Duration (R - D): 0.1599 seconds
Duration: 0.6800 containment intervals: {+/- 0.0371} seconds
Duration: 0.9500 containment intervals: {+/- 0.0873} seconds
Duration: 0.9973 containment intervals: {+/- 0.2077} seconds
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I used TME apertures on all stars. For ref1, there are many single point drops, for an unknown reason. Not so for the target nearby, nor for ref2, which was used as the reference star for these reductions |
No other frames went to zero, and no other two consecutive frames even dropped to 50% level. Only the 4 frames (2 integrations) labelled went to zero, and were detected. |
PyOTE was told to find the best event that was at least 2 integrations long. The mag drop was input as 4.8 for the "W" bandpass (Watec bandpass estimate, halfway from V to R). |
Zoomed in. The "no-star" (sky) level was not TME but a 4 px circular aperture in a region near the target which has no C2A stars and looked blank on the video. |
False positive test. Red bar at 2 sigma estimated. |
Reference calibrated light curve |
Zoomed in. The apparent event was 4 seconds or almost 10 asteroid diameters late. |
2nd Analysis done in July: Perhaps the 1st analysis' TME apertures were too tight and too much starlight slipped over the edges? So I then tried a more generous circular aperture for all stars. The result was worse for all stars, not worth plotting. The initial TME analysis done in July also had worse wavy star curves than the Nov 9 re-analysis, which also used TME but over perhaps a different number of frames for the 'finder' (?). In either case, the TME apertures gave the steadiest light curves for all ref stars and target. The circular aperture results images were deleted from my website to avoid confusion.
Note: I re-did the analysis from scratch on Nov 8/9, using TME apertures and a 66 frame Fourier 'finder' to determine the masks for the stars. There was no wind or other disturbances to blur over a decent analysis. The folder based on this new analysis is named by PyMovie as usual. In order to get PyMovie to work, I first had to rename the original folder made by PyMovie as 20240703Rogerbyrd1 ie i added a "1" to the name. Then PyMovie would work, making a new folder 20240703Rogerbyrd
Looks like I got a miss for Rogerbyrd, no apparent event. I recorded at 8x by mistake, so I might have missed a short event, however, the detectability test in pyote says: Undetectability reached at magDrop: 5.00 duration=: 0.100. An event of duration 0.150 seconds with magDrop: 5.0 is likely detectable. So supposedly I could have detected an event as short as 0.1 seconds, and max for this was .42 sec, and I wasn't far from center line. This may be one of those events where the prediction was off. But if either of you got an event, that would be ...interesting.
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No hint of any events on Kirk's light curve, from south of my track. |
RN: It is clear from my and Kirk's ~centerline positions and good S/N results that the tight confidence limits, high probability=99.99% odds of a 'hit' for his and my positions, was unwarranted. Something made this asteroid's orbit determination nowhere near as accurate as implied by the OWc predictions. Therefore, we must leave open the possibility of an event rather far off the nominal prediction.
I had nearly identical results. Recorded at 4X with nothing obvious, but on playback on our big TV, a couple short scintillation blips at about the predicted time. One of them could have been a very brief occultation that I assume the software might ferret out.
