California/Az were the favored locations: highest in the sky, darkest sky.
The centerline was near Ojai, south of Carrizo Plain. Quaoar is 100 km across.
This event slipped past my awareness. Good thing that Dunham passed this along to me on 6/17. Weywot is 100km across; decently large. The predicted path goes through Carrizo Plain and the centerline is farther south, which may be the area we'd prefer to try for. I'm checking camp areas. The odds of the event a "hit" on the centerline is 56%, so the chance of a miss is significant. We'd want to separate well enough to get higher odds of a hit from one or the other of Kirk and I. It's close to L.A. and I would expect if it gets some attention, there may be more stations who will appear. The event was not tagged and so did not show up in many observers' lineup.
Here's the LuckyStar prediction site, with a good star field map and full stats. But, no UT prediction for the event. Max duration = 4.1s, Altitude at midnight from SoCal = 35 degrees. Due south. From the map below at left, I believe the event is some minutes after 7:52UT or 12:52am, but how far after I do not know yet.
California/Az were the favored locations: highest in the sky, darkest sky. |
The centerline was near Ojai, south of Carrizo Plain. Quaoar is 100 km across. |
The LCD chip image. Pretty crowded, and the target star is the smallest image, nominal UCAC4 magnitude = 16.2 |
Good choice to only plot SAO stars. The bright pair at top provided the search image and that worked well at the scope. |
Q70 eyepiece view. You can see why I chose instead to pull back one more level and get only the bright SAO stars. Otherwise, it's lost in the thousands of stars in this part of the Scutum Star Cloud |
Zoomed in a bit. VERY crowded |
The Sloan Digital Sky Survey (SDSS) close up image of the target area. |
Given the effort level needed to try to get observations of this event, it was definitely called for to make use of a clear moonless night that fell into our laps, and see if our equipment could really get this faint target. I met Kirk Bender at 10:45pm. Our plan was to try integrations on the target using various combinations of optics and parameters. There was also a low-probability asteroid event at midnight, which would also provide an opportunity for more practice and a bit of data as well. We set up on the bike path entrance to Wilder Ranch State Park, which gave us a view over the south (west of the light dome of Santa Cruz) and also avoiding oncoming headlights on Empire Grade. I found the target fairly easily in the eyepiece by 11:15pm. There was no fog or clouds, but the air was cool and moist just the same. There was no fog in Santa Cruz below, all night, in fact.
I used the following settings:
* 64x integration
* Gamma = 1.0
* Gain = 41 (maximum)
* Sharpness=4
* f/3.3 reducer, except for the last image below, when I removed the reducer and images at f/10 focal ratio.
PyMovie screen shot showing the target area, much smaller than the chip's coverage. The faint target was between two much brighter 13th mag stars, and just a few arcsec from a 15.8 mag star to its right. The target was a dim hit above the background |
I used two tracking stars, with dynamic apertures. 64x setting was the maximum setting that would be useful to really be sure of an occultation. That's about 1 second integration, for an event which would last at most 4 seconds. The light curve for the target and for the sky were not significantly different. |
The target light curve. Hugs zero pretty well. |
The blankest sky I could find, looks quite similar. This and the prior 3 images are all using the f/3.3 reducer. |
The star field was so crowded, I had a hard time seeing the target area at the scale provided by the f/3.3 reducer, so I tried removing the reducer and operating at f/10. The target was now so lost in the "sky" that I could not see it. This is instead a stack of 333 frames using the "finder" option in PyMovie. I even had to advance through several seconds of video just to find an integration which showed the target at all (above). It looked easier to see by eye as it was being recorded, as the brain unconsciously added all past frames into memory and the faintest wisp gets interpretted by the brain as significant, even when it is not. |
Second night of testing: June 21 4am.
After I recorded a successful occultation by Hilda, I did more imaging of the Weywot target, this time trying 128x integration and lowering Gain to 30. I also tried 64x again. No integrations showed the target. The sky was brighter, as I was looking over Santa Cruz instead of over the darker north coast in the earlier tests above. I tried lowering sky noise by lowering gain and raising integration. It did not help. The air was dry and the seeing was a bit better than at upper UCSC. That didn't help much.
The Verdict:
This star had me hopeful, with an expected r=14.6 magnitude. But it's UCAC4 visual magnitude is 16.2, and that's about what it looked like. The color image shown on the LuckyStar data from SDSS does show it's more reddish than some other stars. But it didn't seem to help much. The "seeing" was not ideal, but certainly now awful on this test night. It might be better in Carrizo Plain, but possibly not. Since there was no radiation fog happening, I doubt there was significant convective turblence tonight. The sky might be darker in Carrizo, but the SE is a significant light dome from LA area lights. I would expect the sky brightness at Carrizo will be a bit better than we had, but not likely so much better as to change my verdict: This particular star, this event, is just not do-able in an 8SE telescope. I note that the Quaoar event of Aug '22 was a positive for Kirk and I, but the star's nominal magnitude then was 15.2, not 16.2. Also, the event lasted more than 25 seconds, giving the small Signal a chance to add up. Our event for June 22 only lasts 4 seconds, and the 32x we used in 2022 is not able to show the target.
The Nantong Occultation.
Kirk and I halted our preliminary experimentation at 11:30pm to give time to get the Nantong occultation at 12:02am. It's got a separate page for the results. After we returned home, we got a bit of sleep and then got up for the Karolinum occultation, which had a decent chance of 41% for an occultation for this low rank event. But, Kirk and I both successfully recorded a "Miss".
