This is a high value event as we have the possibility of spotting an event by it's moon. I don't know where the moon shadow prediction places it, or if we know the orbit well enough, or even the existence firmly, but it is listed on the OWd feed as a binary or even triple asteroid. It's a long event, 13.2 sec, but shallow, only 0.4 mag drop. The event is very close to M35 in Gemini, less than an eyepiece field away.
Alt=22, Az=75, at the foot of Gemini, 1 degree from M35, and closer to open cluster IC 2157
Kirk, Karl and I at our homes are each only about 1 mile apart from each other's tracks. I decided to escape poor visibility from home and escape fog, and get this from Twin Gates upper UCSC.
Karl did not try this one.
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I tried this from Twin Gates, on the eastern side parking spot, near the gate. I forgot to click 'options' and change the default EIA resolution to PAL resolution, so there is only 640x480 pixels. That caused the OCR boxes to be off quite a bit. But since OCR reading is terrible anyway and I must always use manual time stamps when I get to PyOTE, it really didn't matter, otherwise. I used 8x. And I did not change the default mask size of 3.2px. Static circular apertures. And, there was no "black bar" issue visible during the reductions watch on screen.
magDrop report: percentDrop: 29.6 magDrop: 0.381 +/- 0.070 (0.95 ci)
DNR: 1.07
D time: [09:18:19.1004]
D: 0.6800 containment intervals: {+/- 0.3496} seconds
D: 0.9500 containment intervals: {+/- 1.3347} seconds
D: 0.9973 containment intervals: {+/- 3.1870} seconds
R time: [09:18:35.1003]
R: 0.6800 containment intervals: {+/- 0.3496} seconds
R: 0.9500 containment intervals: {+/- 1.3347} seconds
R: 0.9973 containment intervals: {+/- 3.1870} seconds
Duration (R - D): 15.9999 seconds
Duration: 0.6800 containment intervals: {+/- 0.6370} seconds
Duration: 0.9500 containment intervals: {+/- 1.8603} seconds
Duration: 0.9973 containment intervals: {+/- 3.8848} seconds
The most likely candidate for a moon event is shown as one of the zooms on PyOTE. Given the small drop, it makes it difficult to evaluate. I will wait for Kirk and Karl's data to decide if there's support for it. It's about 4 diameters after the main event.
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I trimmed out the main event and then asked PyOTE to find an event in this area, and this is the result |
NIE test is only 0.8 sigma for the moonlet candidate |
PyOTE found the potential moonlet drop, after I trimmed out the main occultation:
magDrop report: percentDrop: 21.9 mag
Drop: 0.268 +/- 0.127 (0.95 ci)
DNR: 0.79
D time: [09:19:35.8999]
D: 0.6800 containment intervals: {+/- 0.7173} seconds
D: 0.9500 containment intervals: {+/- 2.4008} seconds
D: 0.9973 containment intervals: {+/- 6.0246} seconds
R time: [09:19:39.5799]
R: 0.6800 containment intervals: {+/- 0.7173} seconds
R: 0.9500 containment intervals: {+/- 2.4008} seconds
R: 0.9973 containment intervals: {+/- 6.0246} seconds
Duration (R - D): 3.6800 seconds
Duration: 0.6800 containment intervals: {+/- 1.0433} seconds
Duration: 0.9500 containment intervals: {+/- 2.9933} seconds
Duration: 0.9973 containment intervals: {+/- 6.3147} seconds
Kirk's data convinces me this is just a "noise event" despite being detected and being of reasonable duration and position relative to Sylvia. Kirk had a clear miss at this time and only 6% of the diameter of Sylvia away from me.
Report submitted 9/28/25
I got a 15.2 sec event for Sylvia, 4x from Sunlit lane. I don't see a second event at the time you suspect yours though, see my graphs. By the way, Sylvia isn't just a binary, it's a trinary! Two known moons.
magDrop report: percentDrop: 30.2 magDrop: 0.390 +/- 0.066 (0.95 ci)
DNR: 0.88
D time: [09:18:19.5883]
D: 0.6800 containment intervals: {+/- 0.2300} seconds
D: 0.9500 containment intervals: {+/- 0.8537} seconds
D: 0.9973 containment intervals: {+/- 2.0799} seconds
R time: [09:18:34.8033]
R: 0.6800 containment intervals: {+/- 0.2300} seconds
R: 0.9500 containment intervals: {+/- 0.8537} seconds
R: 0.9973 containment intervals: {+/- 2.0799} seconds
Duration (R - D): 15.2150 seconds
Duration: 0.6800 containment intervals: {+/- 0.4087} seconds
Duration: 0.9500 containment intervals: {+/- 1.2082} seconds
Duration: 0.9973 containment intervals: {+/- 2.6241} seconds
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The vertical line is the time of my possible 2nd event |
Zoomed in. Clearly, no occultation here. |
NIE test on the main event. Passes nicely at 11 sigma. |
KIrk and I were about 6% of the diameter of Sylvia apart, in tracks. 6% of the duration time for Sylvia is .06 x 15s or 0.8 seconds. But my possible 2nd event is 3.7 seconds. What are the odds that I'd have a valid 3.7s event only 0.8s away from a clear miss? Very unlikely. It would take a very oblong asteroid aligned favorably for me and missing Kirk. I conclude that my 2nd event is not credible.
