Occultation event with (4057) Demophon, event index number 3901
Regions able to see the event: SAmericaN
Geocentric closest approach at 2026/07/28 21:39:17 UTC
J2000 position of star is 11:48:04.1 +02:13:23
Equinox of date position of star is 11:49:25.9 +02:04:31
Star is 122 degrees from the moon. Moon is 99% illuminated.
Stellar brightness G=14.4, apparent brightess of occulting body is G=16.1
Use an exposure time of 0.35 seconds with the standard RECON-QHY system.
SNR of 8.3 per integration for unocculted signal
Expected flux drop is 83% with SNR of 6.9 for the occulted depth (per occulted point)
Apparent velocity is 31.6 km/sec on the sky relative to the star, or, 26.8 arcsec/hr.
Position angle of asteroid motion is 115.1 degrees
The recommended exposure time corresponds to 11.0 km per image.
The 1-sigma error in the time of the event is 1.0 seconds.
The 1-sigma cross-track error in the shadow position is 24.7 km.
The sky-plane scale is 4240.5 km/arcsec.
Diameter estimates:
53.2 km assuming a 5% albedo, maximum of 1.7 sec for a central chord
21.7 km assuming a 30% albedo, maximum of 0.7 sec for a central chord
Cross-track diameter of 45.7 km used for deployment plan.
Star training set for 4057_Demophon, (2026/07/28 21:39UT) Object RA Dec mag sep mel Regulus 10:09:47.1 +11:50:11 1.3 26.55 148 Denebola 11:50:24.8 +14:25:24 2.1 12.35 126 5Bet Vir 11:52:04.7 +01:36:54 3.6 0.81 121 PPM 158245 11:51:08.5 +02:05:02 8.0 0.43 121 PPM 158212 11:48:47.3 +01:51:56 8.9 0.26 122 4057_Demophon 11:49:25.9 +02:04:31 16.1 121 Positions are for equinox of date
Star training set for 4057_Demophon, (2026/07/28 21:39UT) Object RA Dec mag sep mel Regulus 10:08:21.9 +11:58:02 1.3 26.55 148 Denebola 11:49:02.7 +14:34:16 2.1 12.35 126 5Bet Vir 11:50:43.0 +01:45:46 3.6 0.81 121 PPM 158245 11:49:46.7 +02:13:54 8.0 0.43 121 PPM 158212 11:47:25.5 +02:00:48 8.9 0.26 122 4057_Demophon 11:48:04.1 +02:13:23 16.1 122 Positions are for J2000