Occultation event with (11509) Thersilochos, event index number 4109
Regions able to see the event: US,RECON
Geocentric closest approach at 2026/08/27 11:15:50 UTC
J2000 position of star is 05:57:27.8 +11:08:07
Equinox of date position of star is 05:58:56.8 +11:08:11
Star is 123 degrees from the moon. Moon is 99% illuminated.
Stellar brightness G=13.5, apparent brightess of occulting body is G=15.9
Use an exposure time of 0.17 seconds with the standard RECON-QHY system.
SNR of 9.8 per integration for unocculted signal
Expected flux drop is 90% with SNR of 8.9 for the occulted depth (per occulted point)
Apparent velocity is 25.9 km/sec on the sky relative to the star, or, 23.4 arcsec/hr.
Position angle of asteroid motion is 108.2 degrees
The recommended exposure time corresponds to 4.4 km per image.
The 1-sigma error in the time of the event is 0.5 seconds.
The 1-sigma cross-track error in the shadow position is 25.2 km.
The sky-plane scale is 3985.1 km/arcsec.
Diameter estimates:
55.0 km assuming a 5% albedo, maximum of 2.1 sec for a central chord
22.4 km assuming a 30% albedo, maximum of 0.9 sec for a central chord
Cross-track diameter of 50.0 km used for deployment plan.
Star training set for 11509_Thersilochos, (2026/08/27 11:16UT) Object RA Dec mag sep mel Betelgeuse 05:56:36.9 +07:24:35 0.4 3.77 121 Bellatrix 05:26:33.7 +06:22:18 1.6 9.31 114 PPM 121631 05:58:18.9 +11:31:20 5.9 0.42 122 PPM 121649 05:58:46.3 +11:26:39 8.4 0.31 123 PPM 121674 05:59:45.5 +11:06:25 9.2 0.20 123 11509_Thersilo 05:58:56.8 +11:08:11 15.9 123 Positions are for equinox of date
This table contains the target star visibility for registered US sites that are relevant for this occultation. This list has been filtered to only those sites that can see the field and are within range of the shadow given the uncertainties. The observing time range has been calculated to cover the time of the event at each site with allowances for the event timing uncertainty plus time for obtaining a pre and post event baseline lightcurve. This set of stations has a 0.0 % chance of getting at least one chord. There is a 0.0% chance of 2 or more chords assuming clear weather for all.
| Site Name | Site mid-time (UT) |
Sun alt (deg) |
Sky | Moon | Star alt (deg) |
Star az (deg) |
Target | Observing Time | Xtrack (km) |
Prob |
|---|---|---|---|---|---|---|---|---|---|---|
This table contains the target star visibility for registered RECON sites that are relevant for this occultation. This list has been filtered to only those sites that can see the field and are within range of the shadow given the uncertainties. The observing time range has been calculated to cover the time of the event at each site with allowances for the event timing uncertainty plus time for obtaining a pre and post event baseline lightcurve. This set of stations has a 99.7 % chance of getting at least one chord. There is a 82.9% chance of 2 or more chords assuming clear weather for all.
| Site Name | Site mid-time (UT) |
Sun alt (deg) |
Sky | Moon | Star alt (deg) |
Star az (deg) |
Target | Observing Time | Xtrack (km) |
Prob |
|---|---|---|---|---|---|---|---|---|---|---|
| Kamloops | 11:12:30 | -16.8 | AT | Up | 23.8 | 101.8 | Low | 11:09:26-11:15:26 | 128.5 | 0.000 | Kelowna | 11:12:30 | -16.9 | AT | Up | 24.5 | 102.2 | Low | 11:09:25-11:15:25 | 47.0 | 0.150 | Peachland | 11:12:29 | -17.1 | AT | Up | 24.3 | 101.9 | Low | 11:09:24-11:15:24 | 37.0 | 0.260 | Summerland | 11:12:29 | -17.1 | AT | Up | 24.4 | 101.9 | Low | 11:09:23-11:15:23 | 22.2 | 0.445 | Penticton | 11:12:29 | -17.1 | AT | Up | 24.5 | 102.0 | Low | 11:09:22-11:15:22 | 15.4 | 0.521 | Oliver | 11:12:28 | -17.4 | AT | Up | 24.6 | 101.8 | Low | 11:09:24-11:15:24 | -19.2 | 0.484 | Anarchist Mountain Observatory | 11:12:28 | -17.4 | AT | Up | 24.8 | 101.9 | Low | 11:09:20-11:15:20 | -36.3 | 0.273 | Victoria | 11:12:23 | -19.7 | Dark | Up | 22.2 | 98.4 | Low | 11:09:19-11:15:19 | -70.5 | 0.027 | Okanogan | 11:12:27 | -17.9 | AT | Up | 24.7 | 101.4 | Low | 11:09:19-11:15:19 | -99.6 | 0.001 | Brewster | 11:12:26 | -18.2 | Dark | Up | 24.7 | 101.1 | Low | 11:09:17-11:15:17 | -125.9 | 0.000 | Manson/Chelan | 11:12:25 | -18.5 | Dark | Up | 24.5 | 100.8 | Low | 11:09:17-11:15:17 | -145.5 | 0.000 | Wenatchee | 11:12:24 | -18.9 | Dark | Up | 24.4 | 100.4 | Low | 11:09:17-11:15:17 | -192.2 | 0.000 |
Star training set for 11509_Thersilochos, (2026/08/27 11:16UT) Object RA Dec mag sep mel Betelgeuse 05:55:10.3 +07:24:26 0.4 3.77 121 Bellatrix 05:25:07.8 +06:20:58 1.6 9.31 114 PPM 121631 05:56:49.6 +11:31:14 5.9 0.42 122 PPM 121649 05:57:17.1 +11:26:35 8.4 0.31 123 PPM 121674 05:58:16.5 +11:06:23 9.2 0.20 123 11509_Thersilo 05:57:27.8 +11:08:07 15.9 123 Positions are for J2000