Occultation event with (11509) Thersilochos, event index number 4171
Regions able to see the event: SAfrica
Geocentric closest approach at 2026/09/04 03:34:59 UTC
J2000 position of star is 06:01:51.3 +10:44:41
Equinox of date position of star is 06:03:20.1 +10:44:35
Star is 28 degrees from the moon. Moon is 52% illuminated.
Stellar brightness G=15.5, apparent brightess of occulting body is G=15.9
Use an exposure time of 0.50 seconds with the standard RECON-QHY system.
SNR of 4.4 per integration for unocculted signal
Expected flux drop is 59% with SNR of 2.6 for the occulted depth (per occulted point)
Apparent velocity is 23.2 km/sec on the sky relative to the star, or, 21.3 arcsec/hr.
Position angle of asteroid motion is 111.9 degrees
The recommended exposure time corresponds to 11.6 km per image.
The 1-sigma error in the time of the event is 0.7 seconds.
The 1-sigma cross-track error in the shadow position is 24.2 km.
The sky-plane scale is 3912.2 km/arcsec.
Diameter estimates:
55.0 km assuming a 5% albedo, maximum of 2.4 sec for a central chord
22.4 km assuming a 30% albedo, maximum of 1.0 sec for a central chord
Cross-track diameter of 50.0 km used for deployment plan.
Star training set for 11509_Thersilochos, (2026/09/04 03:35UT) Object RA Dec mag sep mel Betelgeuse 05:56:37.0 +07:24:35 0.4 3.72 29 Bellatrix 05:26:33.8 +06:22:18 1.6 10.08 25 PPM 121823 06:04:54.2 +11:40:41 6.0 1.01 27 PPM 121844 06:05:37.3 +11:00:44 8.2 0.62 28 PPM 121753 06:02:29.9 +10:24:01 8.6 0.40 28 PPM 121796 06:03:46.4 +10:40:09 11.1 0.13 28 11509_Thersilo 06:03:20.1 +10:44:35 15.9 28 Positions are for equinox of date
Star training set for 11509_Thersilochos, (2026/09/04 03:35UT) Object RA Dec mag sep mel Betelgeuse 05:55:10.3 +07:24:26 0.4 3.72 29 Bellatrix 05:25:07.8 +06:20:58 1.6 10.08 25 PPM 121823 06:03:24.8 +11:40:51 6.0 1.01 27 PPM 121844 06:04:08.3 +11:00:55 8.2 0.62 28 PPM 121753 06:01:01.3 +10:24:05 8.6 0.40 28 PPM 121796 06:02:17.7 +10:40:16 11.1 0.13 28 11509_Thersilo 06:01:51.3 +10:44:41 15.9 28 Positions are for J2000