Reductions of the Ninina Occultation

Sept 10, 2017


Despite iffy weather predictions, the weather was perfect. Clean skies, but the expected point to point brightness scattering due to seeing at only 21 degrees altitude soon after sunset. I set up at my planned station, a hundred yards or so up a dirt road 3 miles east of Silver Springs, NV, off Hwy 50. There was no wind.


The LiMovie video capture screen shot. I used the standard 5/7/25 sizes for the photometry radii, chose the fainter star at left for trackig and photometry both. The target is the very faint image near center

The beginning of the csv file, plotted, for the case of using no psf for tracking or photometry, as some recommend. The poor seeing made it easy to see where the blocks of integrations happen. Highlighted is the beginning of an obvious block. Frame 17/(4 pts per integration) = 4 with remainder 1, so N=4 and offset=1, for analysis in OCCULAR

Here's LiMovie's light curve showing the comparison star (purple) and target (blue). The occultation seems quite unambiguous

Zoomed in on just the occultation, light curve from OCCULAR before block'ing with offset.

After blocking, and running the MaxFOM, here's the full light curve, which includes data from 1 minute before to 1 minute after the 3.4 second occultation event.

Zoomed in on the OCCULAR light curve with T-statistic plotted as well, showing the occultation, consistent with zero light level at the bottom, which isn't surprising considering the limiting magnitude was about 14.85 (determined by OCCULAR) and the asteroid is v=15.0.

Monte Carlo run showing the D and R solutions. 90% are very consistent, a few are off. Given how sharp is the D and R and the apparent diffraction spikes in brightness at D and R, I'd expect high confidence sharp convergence on the D and R

D and R distribution of determinations from the 100 Monte Carlo trials in OCCULAR.

The noise histogram looks decently Gaussian.

The OCCULAR final report output. Confidence given as 100% which seems right. Here's a link to the .csv version.

My site, at a tiny wide spot in this dirt road. Google Earth coordinates are in excellent agreement down to the resolution of the map, with what the GPS satellites read on my camcorder IOTA VTI insertion screen


W. Longitude: 119d 09m 27.588s
N. Latitude: 39 26' 01.104"

Elevation: 4306 ft (from Google Earth, and 4295 ft according to the GPS reading. I'll take the GE reading as the most reliable. That's after adding 4 ft to get to the elevation of my telescope, since the altitude was so low (21 degrees) and not to have to do that geometric correction for the intersection of the light path with the ground.

Link to the .xls official report sent to Brad Timerson on 9/18/17 and also sent was the .csv file for 'no psf tracking/photometry' here