The Occultation of a 14.2 star by the Asteroid 1999-RM11

July 7, 2022 at 1:28:52am

This is a tough event! 14.2 magnitude, will require integration and clean skies. 4.1 second duration, full drop as far as our equipment is concerned. It's 26 degrees up in Az 193. There's no other observers signed up.

Results:

Kirk and I tried this one from Bonny Doon. I was at Sunlit Lane at the end of the air strip, Kirk was at his same site just 1/2 mi north of the bike path at UCSC upper meadow. We had clear skies and recorded the proper fields,

Nolthenius

This path was centrally across the Santa Cruz / Santa Cruz Mtns area unlike the event 2 hrs earlier. So, to separate adequately from Kirk's chord, I drove up to Sunlit Lane at the end of the airstrip, and had perfect conditions and excellent tight seeing to get this faint 14.2 star surprisingly easily. I first analyzed and forgot to do a " apply 'line noise' filter in vertical direction'. And the event was noisy and barely above the 0 false positive threshold. I redid it, used a 4.5 pixel aperture, given the good seeing, instead of the 6.8 pixel aperture of the first attempt, which may have also gotten some surrounding stars' contamination in this rich star field next to the top of the Teapot of Sagittarius' Milky Way. The second PyMovie run was much more successful, after applying the vertical noise filter.

The 14.2 star looks nicely visible here. BUT realize these were perfect conditions - no moon, laminar inversion layer atmosphere with no wind, very dark skies above the fog deck covering Santa Cruz, and 2,000 ft up in the mtns. And at 32x integration setting.

Target star light curve, 16 points per integration.

I used 2 widely separated bright stars for tracking in order to null any field rotation.This is one of them. Nicely quiet light curve.

The composite light curve from PyMOvie of the two tracking stars, the target star, and also shown is the zoomed tracking square on the target star.

RN PyOTE Analysis

I ran this at 32x, so that's 1/2 second integrations. Long, but I wanted to be sure to see the target on each frame. It was a last second decision; 16x or 32x, and I went with 32x. I could have done 16x I'm sure. But for a 14.2 star, that sounded like I was really asking for a lot, so I backed off. I had a 3.99s event, good enough for 8 integrations of occultation and a confident event.

The 3 light curves inside PyOTE, with integration applied

zero chance of a false positive

3.99 second event

Kirk Bender

Kirk observed from the open field about 1/3 mile north of the bike path crossing of Marshall Field (Upper Meadow UCSC). He also got a solid occultation. I believe his Watec camera is just a little better than mine, not suffering from the vertical banding noise for one thing. He got a faster cadence shorter integrations and tighter timing accuracy.