This is a relatively bright, very long event which is a good candidate for hunting for moonlets. It's a low number asteroid therefore with a long history of astrometry and shown as very high rank. It's a "sure thing" and likely not of great value for further improving the orbit. But a moonlet discovery would allow mass and density calculations which are independent of any hints from reflection spectra. The path stretched from Silicon Valle on the northern limit y to deep into Monterey County. All of our Santa Cruz team is well inside the shadow, and it's not a sleep-killer. Yanzhe Liu is right on the norther limit and could provide a very good astrometry position, along with Pran Hyseni
I'm tentatively planning on getting it from Cabrillo Observatory as part of a training session for my new T.A.
Alt=59 Az=south
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Jordan, helping organize tthe work bench for some needed use putting together the OccBox for her. |
Set up for the Meliboea occultation. |
Reviewing the recording. Unlucky the big cloud got most of this event, but I believe I was able to extract the R as the cloud passed. |
Kirk and I got recordings. Karl was unable to ID the field. Not yet known if Bernard tried or got this one.
I set up out of my RAV4 from just outside the dome building at Cabrillo Observatory. We had fast moving low thick clouds all evening, as Jordan and I worked on getting the Observatory ready for the new semester with organizing, and I on getting the new OccBox ready for Jordan's use. Neither project totally completed, but good progress. I also examined the new CPC11 Celestron scope with geology loup and could see no evidence of corrosion or damage or alignment trouble on the prongs of the 'hand controller' connector. The hand controller I used, my own, has no trouble with operating the 8SE I use for occultations. And most buttons worked OK on the CPC11". But the "up" arrow button is very intermittant. I've concluded that the trouble is inside and we'll have to pull off the cover to look at the connections inside the 11" before seeing what's needed. Until then, I cannot estimate a value of this donation. The hand controller, I'm now convinced, is not the source of the trouble, nor is the immediate prong connections between hand controller and scope base female connection. The trouble is inside. I found I could get the scope to go in the other 3 directions w/o trouble. But in the "up" arrow direction, the behavior only works sometimes when moving around on the connector. I hope it's just a lose wire inside the base somewhere.
For the Meliboea occultation, Jordan watched and helped as I instructed on how to set up the 8SE. There was a big cloud that covered the area of the sky needed. But I did get a 2-star align on Polaris and Rigel and it went fairly well to the target area. I only got a brief view in the eyepiece, unable to tell where it aimed, And then, the time got very tight and I decided our only chance would be for me to swap in the Watec, make a guess at focus (about 7 CCW turns on the knob), and then wait. Then, a clear patch crossed the area and I could see the focus was not terrible, but the stars were little donuts. I tried to improve the focus but clouds returned. Focusing had to be abandoned, and I turned on the recording, and just hoped I could ID and get On-Target. Less than a minute to go, and the clear sky returned, for long enough to ID the stars (at 8x) and move it to the target. Then I could see the target and see it fade as a cloud came over right around the "D" time, and then clear away about the "R" time.
The D ended up lost in the cloud. Could not recover the D. But the R was (barely) late enough to get it as the cloud cleared. Still there was rapid variable obscuration and so my smoothing interval optimized at a very small 2-point smoothing length. I might have gotten a differennt timing slightly if I'd been able to apply a smoothing of 0 and still used it as a reference star. As is, PyOTE doesn't let you use a 0 smoothing length and still use the ref star as a reference star. The light curve defaults to raw.
My examination integration by integration convinced me that the actual target R was later than determined by PyOTE from RN-PyM2-Meliboea. I now believe it was because the masks were not following immediatly and had to snap into place, and made erroneous comparisons between ref1 and target for the first few frames. So I carefully measured the offset between tracking star and target star using a "finder" image, and then moved the frame position to be at the first confident place I could see the reference star, positioned the aperture/masks, and then clicked "analyze" again. This time, I believe it gave a time I can believe is correct. There is a clear moment of good brightness of the tracking star, at a moment when the target star is still absent. shortly after, the target appears while the ref1 star is faded for several frames, indicating this must be the actual "R".
For completeness, here below is the PyM2 (with likely tracking error at beginning) results. These are NOT the results I accept.
magDrop report: percentDrop: 100.0 (magDrop cannot be calculated because A is negative)
DNR: 9.29
R time: [05:26:53.3620]
R: 0.6800 containment intervals: {+/- 0.0284} seconds
R: 0.9500 containment intervals: {+/- 0.0725} seconds
R: 0.9973 containment intervals: {+/- 0.1351} seconds
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This analysis places aperture and mask on ref1=tracking star as it first appears from behind a cloud, so that no tracking error or measurement error occurs in early frames, then follows it till a deep cloud a minute later. This should give a better calibration on the target star and better measure the R time to agree with the visual look of the frames, seen below.
Sequence of frame captures, showing the target appearing only barely, when the ref star is bright, and then on the next frame when the ref star is dimmer, the target star is much brighter, and stays at calibrated brightness after this time.
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This is the first frame while the ref1 star is near normal cloud-free brightness, The "spike" seen on the light curve. Yet the target looks to be just barely above zero. |
1 integration later, the ref star is dimmer, but the target is now clearly rising. This is the arrival of the R. |
Jan 21
Re-done so I could output the manual-time stamped CSV data vis PyOTE... used RN-PyM3-Meliboea, again used smoothing=2, trimmed to just before the "double cloud" and also trimmed off the first few points, specified the "R" interval ti make sure the first point was higher than the second, and the last point was lower than the full R, so as to provide a proper place PyOTE to set the R, and got the same time as the Jan 10th reduction, but poorer timing accuracies. Whieh I've retained in the IOTA report and shown below...
magDrop report: percentDrop: 69.8 magDrop: 1.299 +/- 0.607 (0.95 ci)
DNR: 3.71
R time: [05:26:54.3282]
R: 0.6800 containment intervals: {+/- 0.0571} seconds
R: 0.9500 containment intervals: {+/- 0.1612} seconds
R: 0.9973 containment intervals: {+/- 0.5526} seconds
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did a pre-point with the 8SE, and it worked! Looks like a positive. I got a 9.5816 sec event for Meliboea using the C8 and Astrid unattended prepoint, at 12fps (5x NTSC Watec equivalent). I was not there, but it appears by the tracking star that there were intermittent thin clouds, however the target event is distinct and centered on the predicted time.
NIE sigma distance 26.7
magDrop report: percentDrop: 74.8 magDrop: 1.495 +/- 0.200 (0.95 ci)
DNR: 2.32
D time: [05:26:45.8291]
D: 0.6800 containment intervals: {+/- 0.0416} seconds
D: 0.9500 containment intervals: {+/- 0.1690} seconds
D: 0.9973 containment intervals: {+/- 0.3965} seconds
R time: [05:26:55.4107]
R: 0.6800 containment intervals: {+/- 0.0416} seconds
R: 0.9500 containment intervals: {+/- 0.1690} seconds
R: 0.9973 containment intervals: {+/- 0.3965} seconds
Duration (R - D): 9.5816 seconds
Duration: 0.6800 containment intervals: {+/- 0.0684} seconds
Duration: 0.9500 containment intervals: {+/- 0.2087} seconds
Duration: 0.9973 containment intervals: {+/- 0.4761} seconds
Jan 7 ~9:26:50 (137) Meliboea From S of rock-dark cold, clear then fast clouds, Got recording at 16X . Had trouble IDing eyepiece view, switched to Watec and started recording just before event. Viewing after, saw about 7 second event. Processing: Two cloud coverings after event. In try (2), I stopped PyMovie analysis before the cloud events = better results in PyOTE.
