This is a very high value asteroid target. Tiny, but a potential Earth Hazard as it's a NEO (Near Earth Object). It will be the target of the Hayabusa 2 Spacecraft Mission, which will do a flyby in 2026 of this object, so an improved orbit and detection of any possible moonlets is extremely important. The path enters the US at Nogales, AZ and tracks steeply NW up through SoCal deserts and exits into the Pacific Ocean at Garrapata State Park south of Carmel on the Big Sur coast. MIRA-OOS is just outside the northern limit of the tracks laid out by David Dunham, the last estimated uncertainty limits. The duration is only 0.12 sec for this 0.50 km asteroid, but for a 9th magnitude star, this is quite do-able at 1x and 1/50th or 1/60th second time resolution. A central occultation at 1x would give 5 or 6 points inside the occultation.
Ideal if MIRA can accomodate as our base, for deployment south and using the big scope; for very high accuracy photometry vs. our 8SE's for timing. If the big scope isn't possible, maybe the 14", or maybe just set up on the grounds our 8SE scopes and at China Camp down the road, and treat our small group with watching MIRA - OOS at work?
Alt=36, Az=148 in Cetus, just a degree below the pair of stars in the dip in the Whale's back.
Friday Oct 24 Update
Weather looks imperfect, but worth a go, I think. Rain is forecast for mid Saturday, but clearing in the late evening when the event occurs. Then more rain on Sunday later. DWD has put together tracks for observers to occupy to get good coverage. The central tracks are going to be covered by the Arizona people including DWD stations. If weather improves, I may still try it. No van, so it would have to be in my RAV4 and the closest location is Garrapata Beach on the Big Sur coast. MIRA is just north of the array of lines, and I will alert Dan Cotton if the telescope is accessible by him.
J2000 target Coordinates
RA= 1hr 51 00s
Dec= -11 38 23"
Jnow On Date Coordinates:
RA= 1hr 52 18s
Dec= -11 30' 34"
Line Assignments for the 2025 Oct 25/26 Torifune occultation
New at 8:20pm on event night; to accomodate altitude/az of target. Kirk is at 5.6N, I will be at 3.5N. There are no other spots with turnouts and altitude requirements without going even deeper into the rest of the stations.
Kirk is at Lat=36 27 23" at Garrapata Bluff Trailhead, wide area of parking to use.
RN is at Lat=36 26 52.5" at a turnout on the right side of the road, probably not marked. But with the target almost straight down the highway.
Northern-most end of the turnout. Measured afterwards I was 37 feet south of the entrance to the trail.
RN Long=121 55 33.40 and Lat=36 26 52.21 and elev=41m
Track assignments updated just before leaving for the event. Not final.
5.5N Kirk Bender
4N Norm Carlson
3.5N Richard Nolthenius
3N Vince Sempronio
2N Ted Blank-1
1N Ted Blank-2
0 Ted Blank-3
1S Dunham-1
2S Dunham-2
3S Dunham-3
4S Dunham-4
5S
6S
The path uncertainty is apparently better than shown here, according to the latest from DWD and shown at right. |
The tracks just miss MIRA-OOS, but it would be a valuable observation just the same. However, the post-storm clouds tend to stick to the mountains and this disfavors Chews Ridge. This will be the last update on the path. |
I'd propose this 6N for Kirk Bender, for easier logistics |
I would take 5N |
 |
 |
Weather update on ECMWF cloud model, as of 2pm Saturday:
https://weather.us/model-charts/euro/california/total-cloud-coverage/20251026-0600z.html.
30% cloud cover at Sobranes Trailhead where I am thinking of trying this event. and along the coast north of their to Monterey. The clouds look worse on the lee side of the mountains, in Salinas Valley, and also where the path is much further south and a longer drive. With clearing from the storm happening from north to south, the Salinas Valley looks like a poor bet.
Final weather update, at 6pm Saturday and for the 11pm event time conditions. The forecast still calls for the clearest (and nearest) sites to be on the Big Sur coast, with only 20-30% cloud cover skies. This is worth a go.
 |
The favorable localized cloud forecast and importance of the event motivated me and Kirk to go for it despite the rain during the day and forecast rain the next day, and the 100% cloud and ground fog cover all around Santa Cruz county. Just before Kirk arrived at my place to carpool down, I realized that the azimuth of the target and the orientation of the steep Big Sur range and road cuts and cypress trees made both of my planned sites very risky or impossible to see the target above local horizon. I search until I found replacements. Kirk at the Garapatta Bluffs Trailhead, and me at another trailhead about a mile further south and halfway between 3N and 4N. Kirk was at 5.5N and would anchor the north end of our distribution. We left Santa Cruz at 8:45pm, and crawled along the freeway Hwy 1 until getting out of the ground fog past Moss Landing for a bit, then back in it in Marina and Monterey. Then, past Carmel and hitting the Big Sur coast, it cleared up, just as the forecast map above suggested. We had near perfectly clear dark moonless skies down to our sites.
We both got good 1x recordings.
I, however, did have variable obscuration, and there were no other stars visible at 1x. I played with gain and settled back at maximum gain=41 since I worried about cloud cover from further south coming in. In order to keep high time cadence and also perhaps see the fain surrounding stars, I adjusted recording contrast to maximum, and could just see the fainter stars. I tried the brightest which was below the target as a tracking star, but 30s before the event the variable light cloud dropped it out of view. I had to re-run through PyMovie and this time only had the tracking star as the target star itself. Despite the variable obscuration, the target was easily visible by eye on the computer screen at all times, and I saw no occultation. The raw light curve below shows no occultation. I set the tracking aperture on the target star but this time as a static 3.2px circular aperture. The target was a dynamic mask aperture.
 |
Pymovie composite light curves. The target is masked twice; once as "target" and once as "track" but as "track" it was a static 3.2px circular mask, and as "target" it was a dynamic mask |
Target star alone, uncalibrated |
In PyOTE. Uncalibrated. |
 In order to remove slowly varying cloud obscuration but preserve the signal of a sharp 0.12s drop to zero for the occultation, I smoothed the target star with smoothing interval of 50 pts (= 1 second for my PAL Watec) and then used it as the reference star. Conclusion - no occultation. |
How I made sure I was at the right locations. I noted the Latitude in my notes for our sites, then used the "Compass" app which shows long/lat, on my iphone |
At Kirk's station |
 |
 |
At my station, some nice Milky Way shots scene shots. |
 |
 |
 |
 |
 |
 |
 |
Observed from track 5.5N at the trailhead for the Garrapata Bluffs Trail, from the coast side parking area. Clear skies, not reduced yet.
Following the IOTA message board and email threads, here is what I see...
5.5N Bender - Observed, report to follow
4N Carlson - No Data: could not get on target in time, plate solving failed
3.5N Nolthenius - Miss
3N Sempronio - probable Miss, will confirm later
2N Ted Blank-1 - Miss
1N Ted Blank-2 - Miss
0 Ted Blank-3 - Miss
1S Dunham-1 - Observed, report to follow
2S Dunham-2 - Observed report to follow
2.5S Robert Jones: Miss
3S Dunham-3 - unsure if on target; reduce later
4S Dunham-4 - No Data: could not get on target in time
5S Robert Jones: Miss
6S
Added; Here's some more information relayed by David Dunham
OCT. 26, around 5:55 UT (Sat. Oct. 25, 10:55pm MST/PDT): A 0.1s occultation of a 9.9s star by (98943) Torifune, a 600m near-Earth asteroid and target of Japan's JAXA Hyabusa2 extended mission. An occultation by Torifune was recorded from one (of 21) stations during a 2023 campaign in Japan, but the star unluckily had poor Gaia data (high RUWE, more than for the Pathenope star), seriously degrading its use for updating the orbit. The current orbit JPL#281 now on OWC (link https://cloud.occultwatcher.net/event/1759-98943-26458-647277-U001970# ) should be good (and our star has a good RUWE value), with rather small path errors, like OWC shows; the object is now just 0.2 AU from Earth, so astro -metric observations from around the world are being collected and used by the JPL Horizons team. Still, we'll want several stations since the nominal error is 8 path-widths due to the small size of the object. This is one of the better events to get a good positive for this spacecraft target. The path passes a few miles south of Ajo, AZ, so we are planning a few-station effort for it there. I hope others can join the effort. We'll be coordinating with Richard Nolthenius' team from Santa Cruz, CA. They will be trying it from south of Monterey on the Big Sur coast of Hwy 1.
