This bright, easy event is on a Saturday night, high rank, and visible from home. The drop is 0.5 magnitudesThe altitude is only 17.6 degrees, though, at azimuth 96. For me, that means if I set up my scope right next to my car's back at the carport, I'll have about 14 minutes after the star rises over the roof of the adjacent structure before the event. The star is bright and I think that's do-able. Best to crank the tripod at full height and get as close to the back of the car as you dare. You might want to set out the VTI box under a wide sky for a good period of time before that, so it can acquire the satellites before you bring it to half-occulted by your apartment. Kirk won't be able to get it from his driveway, but it should be easy to get from the Pogonip Overlook at UCSC, or higher up Empire Grade. But take care not to not get too close to the two tracks already claimed up closer to the limit. However, the moon is near full and only 17 degrees away, so that will make for a bit of challenge since the altitude is so low there'll be more moonlight scattered by the 3x amount of atmosphere down there to deal with. Also, in reductions, note that there are two faint stars very close to the target which will be hard to exclude. Either use a lunar half aperture in LiMovie, or else use a big enough aperture to be sure to include them both consistently through the event, and accept the lower level of drop. That's not my best advice- I'd opt to exclude those two faint stars using the lunar limb aperature.
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A success! Not that surprising. The odds of a hit here were 93%. For the reductions below, I had to deal with the 2 faint stars next to the target very close. I made sure the photometry circle enclosed only the target star, and tried to insure that the sky annulus included both of the faint nearby stars on the star chart. However, those stars were not visible on the playback. I'm fairly sure I included the nearer star, not so sure I included the farther of the two. LiMovie will only let the sky annulus go out to 25 pixels radius, and I think I made the safest choice. I set the Watec on 4x setting, or 2 frames per integration and PyOTE confirmed with identified blocksize=2.
Screen capture of LiMovie |
Full light curve, of comparison (pink) and target (blue) |
raw PyOTE time on the bottom point of this possible satelloid, is 4:13:32.73 |
Kirk set up at the Pogonip Overlook site on the UCSC campus. Weather was good, but at 18 degrees altitude there was scintillation for both of us.
Kirk's LiMovie photometry. He chose to use the dimmer star for nominal comparison star. But the yellow light curve is for the brighter of the remaining stars. Best would have been to use the bright star sitting inside the "F9" at lower left, or re-position so that the bright star I used could be the comparison star. Noise levels are higher with dimmer comparison stars. |
Kirk's complete light curve for his 3 stars. In LiMovie, you can eliminate the plotting of light curves by just clicking on their button in the lower right. In this case, it would have made for a cleaner view of the light curve. |
zoomed in to the occultation itself, which is on the left half of the plot. |
Later in Kirk's light curve, around when we have the suspicious drop in RN's light curve. |
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PyOTE csv file
PyOTE final report
Kirk's data in PyOTE analysis shows a block size of 4, 4 frames per integration = 8x setting on the Watec 910hx. So, his time resolution is half of mine.
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PyOTE csv file for Kirk Bender
PyOTE final report for Kirk Bender
Summary: My data show a 5.9 second event, with 2-sigma error of 0.6 seconds on the duration. Kirk was just 3 miles north of me, but his duration shrank to 4.0 seconds. The deep dip in my light curve at 4:13:32.73 to only 20% of normal is deeper than could be caused by an occultation alone, and must be largely due to scintillation. But I thought it worth checking if it might be due to a satellloid occultation and scintillation. A small satelloid a few miles across might be confirmed by a similar event on Kirk's light curve. His light curve shows no such dip at that time. Also, my light curve points around that time are within the typical scintillation noise although low side, around the time of the deep dip. But there is nothing evident in Kirk's PyOTE light curve to suggest a satelloid occultation. PyOTE did not find a D or R at my suspicious satelloid time. So, we'll consider it noise for now.
