This is one of the brightest occultations of the year for this area. It lasts a full 5.8 seconds on the centerline. Good prospects for probing for any moonlets, as we can do this at 1x. The path is wide and covers all of our team.
Alt=34, Az=173 in Sagittarius, a right-ward extension of "the teaspoon" asterism
The only problem is that its at 2am on a weekday. Hopefully the fog will lift and we can get it from home with minimal sleep loss.
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I set up outside my carport, opposite side of driveway. Got a clear positive at 1x, no drop in gain, left monitor connected. Clear, dry conditions. Kirk, Karl, and Bernard have also reported getting positives. Clear, no wind, no fog, 50 ft east of my carport. Mag 8.7, gain left alone
start 8:57:29, End=9:02:02 UT
long: 122 01 55.00
Lat 36 58 22.66
elev 31 ft
For the first time, I used the "Edge on Disk" method. It was not easy to get to convergence, but eventually the light curve fit the data points very well. First, here is the square wave model solution. Needed because only the Square Wave solution includes the 1-, 2-, and 3-sigma confidence limits.
magDrop report: percentDrop: 99.3 magDrop: 5.329 +/- 0.440 (0.95 ci)
DNR: 6.41
D time: [09:00:02.9368]
D: 0.6800 containment intervals: {+/- 0.0017} seconds
D: 0.9500 containment intervals: {+/- 0.0042} seconds
D: 0.9973 containment intervals: {+/- 0.0083} seconds
R time: [09:00:07.0860]
R: 0.6800 containment intervals: {+/- 0.0017} seconds
R: 0.9500 containment intervals: {+/- 0.0042} seconds
R: 0.9973 containment intervals: {+/- 0.0083} seconds
Duration (R - D): 4.1492 seconds
Duration: 0.6800 containment intervals: {+/- 0.0025} seconds
Duration: 0.9500 containment intervals: {+/- 0.0056} seconds
Duration: 0.9973 containment intervals: {+/- 0.0098} seconds
Confidence limits are not given in these "other models" solutions, and so the 1, 2, 3 sigma confidence must be gotten by a separate run using "square wave", at least as of now, in PyOTE. I noticed that in the optimization procedure, the chord length was optimized in automatic iteration mode mostly by impact angle. The users must, I realized after hours of playing with it, must set the other poorly defined parameters manually, then let it use that as a constraint and find a best solution. So I random walked my way through differing occ duration, impact angle for the D, and star diameter, all by intuition. I finally got a solution that fits both the D and R well, but the star diameters turned out to be rather small than I thought, and I saw a lot of "solutions" that had the R impact angle unrealistically small. Finally, I got a solution with reasonable impact angles of near 45 degrees on D and R and fit the D and R sloping pretty well. The duration was a bit longer than the 'square wave' solution of 4.1492 duration above; at 4.1709 s
Edge-on-Disk Solution:
D: 9:00:02.9042 UT
R: 9:00:07.0841 UT
duration = 4.180 s
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Note the difference between the "D" moment here in the edge-on-disk model, vs the square wave model, where the D is placed at the bottom of the light curve. This above is most realistic. |
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The square wave model, puts the D near the bottom of the light curve after the fade is done. |
The placement of the R in the square wave model, however, isn't much different than that for the edge-on-disk. About mideway up the ramp, which seems realistic. |
Kirk and others, please use my new instructions on how to do the "Edge on Disk" method for getting D and R timings. "Edge on Disk" Instructions
I got a 4.5 sec positive for Gaussia, June 16th, at the Berm, 1x. Initially I had red lines in PyOTE from missing readings. Not just missing timestamps, but missing data lines in the .csv. For some reason, PyMovie was recognizing the timestamps in the .avi but giving errors: "cannot convert float NaN to integer", such as from a divide by zero condition in the calculations, and not writing out the data. I found that if I increased my aperture size from my default size 31 to size 41, I didn't get the errors or missing data. I reported the issue to Bob Anderson.
Re-analysis with Edge-on-Disk method
4.5 sec event. Slightly gradual D and R, used edge on disk model in PyOTE. Reporting D and R from PyOTE edge on disk model, error bars from PyOTE squarewave model.
EOD Timings:
D: 09:00:03.2778
R: 09:00:07.8278
To get confidence limits, must use Square Wave model, which is done below...
magDrop report: percentDrop: 99.3 magDrop: 5.387 +/- 0.592 (0.95 ci)
DNR: 3.64
D time: [09:00:03.2947]
D: 0.6800 containment intervals: {+/- 0.0024} seconds
D: 0.9500 containment intervals: {+/- 0.0067} seconds
D: 0.9973 containment intervals: {+/- 0.0121} seconds
R time: [09:00:07.8306]
R: 0.6800 containment intervals: {+/- 0.0024} seconds
R: 0.9500 containment intervals: {+/- 0.0067} seconds
R: 0.9973 containment intervals: {+/- 0.0121} seconds
Duration (R - D): 4.5359 seconds
Duration: 0.6800 containment intervals: {+/- 0.0036} seconds
Duration: 0.9500 containment intervals: {+/- 0.0083} seconds
Duration: 0.9973 containment intervals: {+/- 0.0148} seconds
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Got a successful observation from home.
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This light curve shows virtually no difference from a "square wave" occultation, in contrast with RN's. Yet RN's occultation was a bit longer, so that angled impact angle would not seem the likely cause. We're pondering what this means... |
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