This is a faint star but long event by a large low-numbered asteroid. In pristine dark skies it should be easy. Note that it is only 3 minutes after another event at Zabriski Point, so we'll have to be quick and it will pay to practice going to each target before having to switch over.
Alt=49 degrees in the West, in Aries
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Only Kirk and I got on the Death Valley asteroid occultation expedition, after Jordan sprained her ankle right before packing to leave with us, and had to cancel. We were the only observers from Santa Cruz.
I successfully got this from the parking lot at Zabriskie Point in Death Valley. Looked to be about 2s long, at 16x through variable cirrus and moonless skies. Some breeze too, but successfully blocked by the large van.
Start 3:51:00 UT, end 3:54:00 UT
NIE test: 4.8 sigma
magDrop report: percentDrop: 69.5 magDrop: 1.291 +/- 0.482 (0.95 ci)
DNR: 2.41
D time: [03:52:30.1293]
D: 0.6800 containment intervals: {+/- 0.1216} seconds
D: 0.9500 containment intervals: {+/- 0.3864} seconds
D: 0.9973 containment intervals: {+/- 1.1908} seconds
R time: [03:52:32.0493]
R: 0.6800 containment intervals: {+/- 0.1216} seconds
R: 0.9500 containment intervals: {+/- 0.3864} seconds
R: 0.9973 containment intervals: {+/- 1.1908} seconds
Duration (R - D): 1.9200 seconds
Duration: 0.6800 containment intervals: {+/- 0.1900} seconds
Duration: 0.9500 containment intervals: {+/- 0.5131} seconds
Duration: 0.9973 containment intervals: {+/- 1.2371} seconds
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An apparent event occured 1 min 50s earlier than the main event. 3 consecutive low readings. I got intrigued, late at night, that this might be real, and got into calculations to judge its plausibility. I didn't do the most obvious observation data check until after this, the next day. But anyway, this was educational and so I am leaving this in the webpage.
This event was 46.25 diameters from the primary occultation. Is this possible? I use physical characteristics of Klio from Wiki here. and the on-line Hill Radius calculator. The result is that R_H = 10,967 km = 133 diameters. Note however that the mass of Klio is quite uncertain since the density is uncertain. If this is a new moonlet, it offers the possibility of determining the mass accurately, once the orbit is determined. The diameter of the moonlet is 0.96s / 3.2s or 0.30 x primary diameters. This would make it about 2.6 magnitudes fainter than Klio, and at a large enough separation and bright enough that it should be straightforward to see in images. The magnitude of Klio was V=13.9, so the moonlet would be about V=16.5 magnitude or brighter, if the same albedo as primary. The diameter of Klio is given on OWc as 52 mas, and so 46 diameters away is 2.39 arcsec, well within the resolution for a good night at MIRA. Perhaps even do-able with a good camera on a 10" scope if a location at good seeing is used, like Bonny Doon.
Kirk Bender observed at 32x, so my 3 points would merge to ~1 point on his recording. Our cross path distance was only 1 mile or 1.62 km. The shadow for Klio was 84km, and the inferred diameter of the moonlet is 0.3 x 84 = 25 km or more, so Kirk and I were close enough that we should have both seen the same event with very similar duration in time.
NIE test: 5.6 sigma after trimming out main occultation and beyond
magDrop report: percentDrop: 89.2 magDrop: 2.418 +/- 2.001 (0.95 ci)
DNR: 3.29
D time: [03:51:43.0896]
D: 0.6800 containment intervals: {+/- 0.0849} seconds
D: 0.9500 containment intervals: {+/- 0.2274} seconds
D: 0.9973 containment intervals: {+/- 0.4920} seconds
R time: [03:51:44.0496]
R: 0.6800 containment intervals: {+/- 0.0849} seconds
R: 0.9500 containment intervals: {+/- 0.2274} seconds
R: 0.9973 containment intervals: {+/- 0.4920} seconds
Duration (R - D): 0.9600 seconds
Duration: 0.6800 containment intervals: {+/- 0.1254} seconds
Duration: 0.9500 containment intervals: {+/- 0.2869} seconds
Duration: 0.9973 containment intervals: {+/- 0.5633} seconds
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Now, having done all this.... an acid test on my own data should be to just see if the target is "normal" during this 1 sec of the occultation. On this measure, this event fails. I got intrigued by the calculating because I knew how to do it and just try and judge plausibility in this way. But... if you look below you see the PyMovie "finder" image with 24 frames = 3 full integrations starting at the time stamp below, which is about the right moment for the first of the 3 low points. I see the target star just fine, at normal brightness. So, it appears to be some form of noise or tracking momentary error (wind?).
24 frame finder begun at the time stamp below, which matches well with the beginning of the 0.96s 3-integration low points suspected as an event. The target star is quite normal. It appears to be a perhaps bit of wind that manage to un-track the target but not un-track the brighter tracking stars or else move them in such a way we had a loss of tracking, is my guess. Whatever the cause, the target star is still there. I will leave the above as a nice bit of science down the rabbit hole that may be useful for future reference. But, follow up for a moonlet is now unwarranted. |
Successfully recorded from about 130 feet up Echo Canyon Road about 2/3 mile north of Zabriskie Point on Hwy 190. Kirk was 1.62 km, cross path, north of RN.
I got a 3.2s event for Klio on Echo Canyon rd, 32x, Feb 14, after the Annalisa event. Target was close to another star so I used small size 11 apertures. Light curves are noisy and there was some wind shake but it smoothed out in PyOTE using the star close to the target and got an event close to predicted time and duration. PyOTE NIE sigma distance was 5.3.
magDrop report: percentDrop: 63.3 magDrop: 1.087 +/- 0.376 (0.95 ci)
DNR: 2.28
D time: [03:52:30.0292]
D: 0.6800 containment intervals: {+/- 0.2157} seconds
D: 0.9500 containment intervals: {+/- 0.6377} seconds
D: 0.9973 containment intervals: {+/- 1.5157} seconds
R time: [03:52:33.2323]
R: 0.6800 containment intervals: {+/- 0.2157} seconds
R: 0.9500 containment intervals: {+/- 0.6377} seconds
R: 0.9973 containment intervals: {+/- 1.5157} seconds
Duration (R - D): 3.2031 seconds
Duration: 0.6800 containment intervals: {+/- 0.3307} seconds
Duration: 0.9500 containment intervals: {+/- 0.8373} seconds
Duration: 0.9973 containment intervals: {+/- 1.8026} seconds
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