Occultation event with (9799) Thronium, event index number 988
Regions able to see the event: Australia
Geocentric closest approach at 2025/05/19 12:06:40 UTC
J2000 position of star is 08:26:44.0 -08:36:15
Equinox of date position of star is 08:27:58.0 -08:41:20
Star is 150 degrees from the moon. Moon is 61% illuminated.
Stellar brightness G=16.5, apparent brightess of occulting body is G=15.5
Use an exposure time of 1.10 seconds with the standard RECON-QHY system.
SNR of 3.0 per integration for unocculted signal
Expected flux drop is 28% with SNR of 0.8 for the occulted depth (per occulted point)
Apparent velocity is 22.0 km/sec on the sky relative to the star, or, 19.8 arcsec/hr.
Position angle of asteroid motion is 4.1 degrees
The recommended exposure time corresponds to 24.2 km per image.
The 1-sigma error in the time of the event is 1.5 seconds.
The 1-sigma cross-track error in the shadow position is 22.5 km.
The sky-plane scale is 4002.2 km/arcsec.
Diameter estimates:
70.8 km assuming a 5% albedo, aximum of 3.2 sec for a central chord
28.9 km assuming a 30% albedo, maximum of 1.3 sec for a central chord
Cross-track diameter of 70.8 km used for deployment plan.
Star training set for 9799_Thronium, (2025/05/19 12:07UT) Object RA Dec mag sep mel Sirius 06:46:16.0 -16:45:09 -1.5 26.05 128 Alphard 09:28:50.1 -08:46:11 2.0 15.04 152 PPM 191380 08:29:33.6 -08:54:08 6.5 0.45 150 PPM 191348 08:28:04.3 -08:33:01 8.5 0.14 150 9799_Thronium 08:27:58.0 -08:41:20 15.5 150 Positions are for equinox of date
Star training set for 9799_Thronium, (2025/05/19 12:07UT) Object RA Dec mag sep mel Sirius 06:45:07.9 -16:43:28 -1.5 26.05 128 Alphard 09:27:35.2 -08:39:30 2.0 15.04 152 PPM 191380 08:28:19.8 -08:49:00 6.5 0.45 150 PPM 191348 08:26:50.3 -08:27:56 8.5 0.14 150 9799_Thronium 08:26:44.0 -08:36:15 15.5 150 Positions are for J2000