Occultation event with (11509) Thersilochos, event index number 4004
Regions able to see the event: Europe
Geocentric closest approach at 2026/08/14 04:09:46 UTC
J2000 position of star is 05:48:43.3 +11:43:44
Equinox of date position of star is 05:50:12.6 +11:44:09
Star is 73 degrees from the moon. Moon is 3% illuminated.
Stellar brightness G=16.1, apparent brightess of occulting body is G=15.9
Use an exposure time of 0.65 seconds with the standard RECON-QHY system.
SNR of 3.1 per integration for unocculted signal
Expected flux drop is 45% with SNR of 1.4 for the occulted depth (per occulted point)
Apparent velocity is 30.4 km/sec on the sky relative to the star, or, 26.7 arcsec/hr.
Position angle of asteroid motion is 103.1 degrees
The recommended exposure time corresponds to 19.7 km per image.
The 1-sigma error in the time of the event is 0.4 seconds.
The 1-sigma cross-track error in the shadow position is 26.2 km.
The sky-plane scale is 4101.4 km/arcsec.
Diameter estimates:
55.0 km assuming a 5% albedo, maximum of 1.8 sec for a central chord
22.4 km assuming a 30% albedo, maximum of 0.7 sec for a central chord
Cross-track diameter of 50.0 km used for deployment plan.
Star training set for 11509_Thersilochos, (2026/08/14 04:10UT) Object RA Dec mag sep mel Betelgeuse 05:56:36.8 +07:24:35 0.4 4.60 72 Bellatrix 05:26:33.6 +06:22:18 1.6 7.93 80 134 Tau 05:51:02.7 +12:39:27 4.8 0.94 73 PPM 121422 05:50:16.7 +12:00:14 6.9 0.27 73 PPM 121417 05:49:57.3 +11:43:23 9.1 0.06 74 11509_Thersilo 05:50:12.6 +11:44:09 15.9 73 Positions are for equinox of date
Star training set for 11509_Thersilochos, (2026/08/14 04:10UT) Object RA Dec mag sep mel Betelgeuse 05:55:10.3 +07:24:26 0.4 4.60 72 Bellatrix 05:25:07.8 +06:20:58 1.6 7.93 80 134 Tau 05:49:32.8 +12:39:04 4.8 0.94 73 PPM 121422 05:48:47.3 +11:59:50 6.9 0.27 73 PPM 121417 05:48:28.0 +11:42:58 9.1 0.06 74 11509_Thersilo 05:48:43.3 +11:43:44 15.9 73 Positions are for J2000