Known moon Remus would not occult for us in Santa Cruz Romulus, according to Ted Swift, had a path also south of the main body and therefore not relevant for us in Santa Cruz. Decently visible star, very long duration, quite do-able, and far from the big moon. It's a known triple asteroid with 2 moons. The moons are most likely south of the main body which means we're unlikely to see either of those moons. We're inside the northern limit, with a likely duration for us of more like 15 seconds or so. The drop is 0.4 magnitudes so that's a bit subtle to see visually, but with a reasonable integration of 4x or 8x, will be quite easy to see for the long duration as compensation. As a triple asteroid, it's a high value target since we can refine the orbit at least with the primary member of the system.
Alt=64, Az = 258, in Taurus just 1 degree away from brilliant 1.8 magnitude El Nath - the northern tip of the horn of the Bull. Use El Nath as an align star and you cannot miss!
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Known moon Remus would not occult for us in Santa Cruz Romulus, according to Ted Swift, had a path also south of the main body and therefore not relevant for us in Santa Cruz. |
Bernard was not able to access this part of the sky from his backyard scope, and has no data.
I observed from home, at 8x, and probably set IOTA VC2.4 recording controls too low a contrast and brightness; light curves look like more noise than I would expect for 8x. But, a solid detection of a 49s event under very clear mild skies. Got a 15s dark video too. However, the D area has an ambiguity. It could be a longer event than I thought, but have a single bright moment that caused me to search for a shorter event.
Kirk Bender was only 8 km north of me and yet had a much shorter 37s event, vs my 49 sec nominal event detection below.
NIE test: 19.1 sigma
magDrop report: percentDrop: 23.8 magDrop: 0.295 +/- 0.027 (0.95 ci)
DNR: 1.31
D time: [06:38:10.1676]
D: 0.6800 containment intervals: {+/- 0.4316} seconds
D: 0.9500 containment intervals: {+/- 2.2909} seconds
D: 0.9973 containment intervals: {+/- 6.0351} seconds
R time: [06:38:59.1273]
R: 0.6800 containment intervals: {+/- 0.4316} seconds
R: 0.9500 containment intervals: {+/- 2.2909} seconds
R: 0.9973 containment intervals: {+/- 6.0351} seconds
Duration (R - D): 48.9597 seconds
Duration: 0.6800 containment intervals: {+/- 0.9343} seconds
Duration: 0.9500 containment intervals: {+/- 3.2769} seconds
Duration: 0.9973 containment intervals: {+/- 7.3580} seconds
Reminder: in the light curves below, the two early drops are due to adjusting the recording brightness and contrast levels in the IOTA VC2.4 software. They are not caused by anything in the sky. Those recording levels were not changed thereafter.
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Possible Moonlet in RN's data,
There is another event, lasting 5 seconds, which has a very similar depth (27%) as the primary event. The 2 known moons of Sylvia have good orbits and their paths were predicted to be south of the main path, while Santa Cruz was at the far north end of the shadow. If it's real, it likely means a 3rd moon. There's no indication of clouds in my data nor in Kirk Bender's. Here's the data...
The secondary event is 5.2 diameters of the primary after the centerpoint of the primary occultation, which is quite reasonable for a moonlet.
NIE test=3.8 sigma
magDrop report: percentDrop: 27.3 magDrop: 0.347 +/- 0.103 (0.95 ci)
DNR: 1.56
D time: [06:44:15.4449]
D: 0.6800 containment intervals: {+/- 0.3034} seconds
D: 0.9500 containment intervals: {+/- 1.5691} seconds
D: 0.9973 containment intervals: {+/- 3.9905} seconds
R time: [06:44:20.4048]
R: 0.6800 containment intervals: {+/- 0.3034} seconds
R: 0.9500 containment intervals: {+/- 1.5691} seconds
R: 0.9973 containment intervals: {+/- 3.9905} seconds
Duration (R - D): 4.9599 seconds
Duration: 0.6800 containment intervals: {+/- 0.6421} seconds
Duration: 0.9500 containment intervals: {+/- 2.2136} seconds
Duration: 0.9973 containment intervals: {+/- 5.1997} seconds
Kirk's data from SkyPark in Scotts Valley rather strongly argues no secondary event for him at that site. We then ask; is the secondary event in my data then in conflict with Kirk's excellent light curve? Here's my calculations:
First, the depth of this event is similar to the depth of the primary event for both Kirk and I. The depth of light loss is about the same as measured in the Watec bandpass for the primary event: ~27% vs my 23% for primary and 21% for the primary for Kirk.
Second, the duration of my event = 4.95 s, is 7.6% of the duration of the main body Sylvia, which has a stated shadow diameter in OWc of 267 km. That corresponds to a moonlet chord length of 20.3 km. Impact angle probabilities for a circular profile are such that this is not far from the maximum, i.e. is roughly the diameter of the possible moonlet. The separation between Kirk's and my tracks was 8.04 km. So if the center of the possible moonlet was just a km or more south of my location, it would be a grazing miss for Kirk. So Kirk's non-event doesn't have much constraint on the reality of this possible secondary event. Kirk's Astrid set up at home, unattended, was untracked and the target drifted out of the field before this secondary event, unfortunately.
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The normalized ref star smoothed curve is in black above target. There is no unusual dip in the ref star light during this 5 second event so a bump or momentary aerosol passage is not indicated. |
NIE Test passes at 3.9 sigma. |
By contrast, here is the other dip in my data which first caught my eye. But note the ref star has an ~identical dip at the same moment - so this is a momentary loss of tracking or other noise. It is not an occultation. |
I got a 36.7028s event for Sylvia, 4x on the 8SE at Skypark. I don't see any secondary events. I'm attaching part of the PyOTE graph zoomed in at 06:44:15 where Rick suspects a second event. I also recorded at home on the Astrid with the 80mm scope, I haven't reduced that yet.
PyOTE NIE sigma distance 22.0
magDrop report: percentDrop: 21.1 magDrop: 0.257 +/- 0.023 (0.95 ci)
DNR: 1.05
D time: [06:38:20.5667]
D: 0.6800 containment intervals: {+/- 0.1888} seconds
D: 0.9500 containment intervals: {+/- 0.7091} seconds
D: 0.9973 containment intervals: {+/- 1.7244} seconds
R time: [06:38:57.2695]
R: 0.6800 containment intervals: {+/- 0.1888} seconds
R: 0.9500 containment intervals: {+/- 0.7091} seconds
R: 0.9973 containment intervals: {+/- 1.7244} seconds
Duration (R - D): 36.7028 seconds
Duration: 0.6800 containment intervals: {+/- 0.3463} seconds
Duration: 0.9500 containment intervals: {+/- 1.0011} seconds
Duration: 0.9973 containment intervals: {+/- 2.2269} seconds
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