Occultation event with (1868) Thersites, event index number 991
Regions able to see the event: Europe
Geocentric closest approach at 2025/05/21 19:45:53 UTC
J2000 position of star is 08:59:47.3 +03:39:14
Equinox of date position of star is 09:01:06.9 +03:33:14
Star is 146 degrees from the moon. Moon is 36% illuminated.
Stellar brightness G=16.9, apparent brightess of occulting body is G=15.6
Use an exposure time of 1.75 seconds with the standard RECON-QHY system.
SNR of 3.0 per integration for unocculted signal
Expected flux drop is 23% with SNR of 0.7 for the occulted depth (per occulted point)
Apparent velocity is 20.5 km/sec on the sky relative to the star, or, 17.3 arcsec/hr.
Position angle of asteroid motion is 11.9 degrees
The recommended exposure time corresponds to 35.8 km per image.
The 1-sigma error in the time of the event is 2.0 seconds.
The 1-sigma cross-track error in the shadow position is 10.7 km.
The sky-plane scale is 4248.1 km/arcsec.
Diameter estimates:
76.2 km assuming a 5% albedo, aximum of 3.7 sec for a central chord
31.1 km assuming a 30% albedo, maximum of 1.5 sec for a central chord
Cross-track diameter of 76.2 km used for deployment plan.
Star training set for 1868_Thersites, (2025/05/21 19:46UT) Object RA Dec mag sep mel Regulus 10:09:43.3 +11:50:32 1.3 18.90 162 Alphard 09:28:50.1 -08:46:12 2.0 14.13 149 18Ome Hya 09:07:18.5 +04:59:22 5.0 2.11 148 PPM 155269 09:00:18.9 +03:33:23 8.4 0.20 146 PPM 155283 09:00:55.9 +03:32:04 9.6 0.05 146 1868_Thersites 09:01:06.9 +03:33:14 15.6 146 Positions are for equinox of date
Star training set for 1868_Thersites, (2025/05/21 19:46UT) Object RA Dec mag sep mel Regulus 10:08:21.9 +11:58:02 1.3 18.90 162 Alphard 09:27:35.2 -08:39:30 2.0 14.13 149 18Ome Hya 09:05:58.3 +05:05:32 5.0 2.11 148 PPM 155269 08:58:59.3 +03:39:22 8.4 0.20 146 PPM 155283 08:59:36.3 +03:38:04 9.6 0.05 146 1868_Thersites 08:59:47.3 +03:39:14 15.6 146 Positions are for J2000