This event is at low altitude rising in the southeast, on the Serpens border very near M16 the Eagle Nebula, but not close enough to use it as a GoTo. However, if you're uncertain of whether the telescope is pointing accurately, you can first try a GoTo M16 and make sure it goes there well, and then go to your target, which is not in a particularly easy field to recognize. Since it'll be rising, you won't have much time between acquisition and event.
At 11.9, this star will actually look like a 13.0 star high overhead because of the altitude extinction. Maybe 4x, or if not, 8x will be good. Magnitudes are given for some stars in the field, to help ID.
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This was a very last minute "go". I didn't decide to even make the planning charts until just before midnight. (Sorry, Karl! I suppose I should have called you instead, but I didn't think you'd want to try such a sleep-disturbing low altitude event). But anyway, weather was perfect (if cold), and it was a Sunday morning and I'd already decided I was not going to do a long run or ride, with some hip pains, so I could afford to sleep in late, and sleep early too, and lose the couple of hours needed to drive up to UCSC for getting a good horizon.
The star was surprisingly visible even at 2x, I went back and forth between 2x and 4x and settled on 2x.... but I didn't expect how poorly the timing results would be. The predicted depth was 1.5 magnitude but the 15 degree convective unsteady air gave me almost no PyMovie selected apertures at 2x. I should have backed off to 4x, but I worried about a short event I might miss if the integrations were too long.
The target star was very noisy, but the event is visible, at center. Notice that PyMovie could not track well enough to make an adapter aperture, and perhaps 90% of the data points are the default round aperture. However, I wateched every reduction frame and the star remained well centered. |
Even the brighter 10.4 tracking star, which had a reliable prescence on every frame, still had enormous twinkling noise. Even though PyMovie did adaptive aperture on nearly all frames. |
The PyMovie composite light curves. The target is in green. The scintillation noise was very high for all stars regardless of brightness. |
My site, at the black "x" |
Was gratified, after seeing how noisy the PyMovie results were, that PyOTE found a pretty solid event, at the correct time, with 0% chance of a false-positive. |
But, I suppose not surprising, the timing accuracies were not great. The observed event time matched the predicted maximum duration of 2.4 seconds. S/N was only 0.84 |
I did some more experimenting. I suspected that either the vertical noise streaks were getting undersampled and so not averaging out adequately, or the star was spreading over more pixels, and so I changed the aperature default from 3,2 to 5,3 and let it still determine the threshold automatically. Nearly all frames still defaulted to the circular aperture. The light curve doesn't look any better, but it reduces better, in better agreement with Kirk's nearby chord and higher statistical confidence. These files are labeled with '4' (I also tried two other attempts which failed but I still kept the photometry .csv files)
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Kirk observed from his driveway, successfull seeing the event at 4x. His data looks much better than mine. It looks from his PyMovie screen capture like he used an aperature circle of 8, which was larger than my old default of 3 and also my newer version "4" size of 5. I suspect my data was noisier because of non-PyMovie or PyOTE issues, but instead the vertical streaks which I've not yet diagnosed. Or a homeless person campfire underneath my optical path? Who knows...
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