The Oenone Occultation and My Trail Running Adventure at Carrizo Plain National Monument

Oct 17, 2015

The nominal instigation of this trip was the occultation of a 9.0 star by the asteroid Oenone, which was targeted by the International Occultation Timing Association IOTA to determine their Annual meeting time and location - Las Vegas NV - over which the narrow path for this event happened. It also crossed Carrizo Plain, with the centerline just 3 miles south of the campsite I've used for years for my Astro 28 Field Astronomy courses here. It's a beautiful overlook in the foothills of the Caliente Mountains. But it's a very long drive, and there were already 37 other astronomers/telescope tracks staked out for this event. I wanted to contribute to the science, but I needed another aspect to completely get me on board. Trail running! It's my most inspiring and favorite of weekend adventures, and I had been intrigued for years to do the long trail run along the ridge tops of the Caliente Mountains to the high point - Caliente Peak - 5,106 ft and the only mountain in San Lius Obispo County which they felt deserved a summit register. The milage is a little fuzzy. One source says it's 14 miles round trip. Another says it's 17. I just measured it on Google Earth using lots and lots of line segments connecting the trail, and if the trail were flat, the total would be 16.91 miles roundtrip. Including the elevation changes raises this by about 0.2 miles or 17.1 miles.

I did my usual Friday swim workout at the gym with Ferrell, and had the car already packed, burrito'd up at Taqueria Vallarta down the street, and ready to hit the road ASAP at 7pm when we got out of the pool. I'd stocked for my listening pleasure along the road some library audio books - E. O. Wilson's "The Social Conquest of Earth", and "True Grit". I arrived at Carrizo Plain at 11:15 pm, and started working my way up the dirt road towards Caliente Ridge road, and it had clearly rained that day, even though skies were now clean and clear. I was amazed to see toads - big ones - hopping all over the road near the abandoned ranch at the turnoff to Caliente Ridge dirt road. Delighted, I felt my inner 8 year-old come to life, who loved finding these unloved creatures in the dank gardens of my youth, and I stopped the car and chased one down, just to grab a few photos for fun, and to identify the species. I didn't know these could possibly live in this desert dry environment.

After a little slipping and sliding in the mud, I made it up to our traditional campsite for Astro 28, about a mile up the road. It's on a ridge, looking down almost 1,000 ft to the plain below, with Soda Lake in the distance, and the scarp of the San Andreas Fault along the opposite side. I got the 10" Meade LX200 scope set up, the video and GPS and video-time inserter gear wired up and ready, then set up my tent and rested a bit before the final push to get the Oenone occultation event at 1:30am. The occultation went well, I found the target without trouble, got great data, and the analysis details are at the bottom of this page.





The Oenone Occultation Analysis

IOTA VTI GPS coordinates from on-screen were
Long = 119 51.2292s
Lat = 35 07.8331'
elev = 897m

Coordinates from Google Earth were different (not sure why; I allowed the VTI plent of time to synch with satellites and get its almanac corrections):
Lat 35d 07' 49.70"
Long=119d 51m 14.20s
Elevation=2946 ft (WGS84 datum).

For the report, I used the Google Earth coordinates as I was very sure exactly where the telescope was placed:

Got the procedures for analyzing video time stamped events using LiMovie and Occular revamped and practiced, so this analysis went quicker than for Eukrate. However, I was not able to get LiMovie to drift track the stars no matter what order I tried clicking the proper controls, except if I used the PSF tracking method. The target and comparison/tracking star were both bright and conditions good, and using the psf method worked fine and is what I used below. I verified that the star reappeared inside the photometry circle, which did not wander during the occultation's 3 seconds.

Here is the LiMovie light curve for the comparison star (pink) and target star/asteroid (blue), using the psf method and allowing all stars to drift independently.

The same - zoomed in

The noise historgram looks fairly Guassian

The LiMovie output .csv file was then analyzed using Occular, from the star mag and color from Steve Preston's data

The Occular-produced "final report". However, the times still need manual correction for the camera delay and VTI correction.

The integration I set for the camera was 2x, (2 fields, or 1 frame), for which the IOTA report template gives a correction for the times to be -0.0334 seconds. The event duration was only 3.445 seconds. The final report .csv sent to IOTA is here . The LiMovie output .csv file is here. And the Sky-plane profile of the single successful track.