Occultation event with (4138) Kalchas, event index number 3743
Regions able to see the event: SAfrica
Geocentric closest approach at 2026/05/13 21:10:45 UTC
J2000 position of star is 11:48:20.1 +00:17:44
Equinox of date position of star is 11:49:41.2 +00:08:56
Star is 165 degrees from the moon. Moon is 12% illuminated.
Stellar brightness G=14.9, apparent brightess of occulting body is G=15.6
Use an exposure time of 0.85 seconds with the standard RECON-QHY system.
SNR of 9.8 per integration for unocculted signal
Expected flux drop is 65% with SNR of 6.4 for the occulted depth (per occulted point)
Apparent velocity is 4.7 km/sec on the sky relative to the star, or, 4.9 arcsec/hr.
Position angle of asteroid motion is 122.9 degrees
The recommended exposure time corresponds to 4.0 km per image.
The 1-sigma error in the time of the event is 6.2 seconds.
The 1-sigma cross-track error in the shadow position is 20.8 km.
The sky-plane scale is 3454.7 km/arcsec.
Diameter estimates:
56.2 km assuming a 5% albedo, maximum of 12.0 sec for a central chord
23.0 km assuming a 30% albedo, maximum of 4.9 sec for a central chord
Cross-track diameter of 46.5 km used for deployment plan.
Star training set for 4138_Kalchas, (2026/05/13 21:11UT) Object RA Dec mag sep mel Spica 13:26:35.2 -11:17:53 1.0 26.65 168 Denebola 11:50:24.2 +14:25:29 2.1 14.28 154 5Bet Vir 11:52:04.1 +01:36:58 3.6 1.58 164 PPM 178587 11:46:22.4 -00:39:54 7.6 1.16 164 PPM 158193 11:47:52.9 +00:12:30 9.7 0.46 164 PPM 158210 11:48:39.8 -00:02:34 10.3 0.32 165 4138_Kalchas 11:49:41.2 +00:08:56 15.6 165 Positions are for equinox of date
Star training set for 4138_Kalchas, (2026/05/13 21:11UT) Object RA Dec mag sep mel Spica 13:25:11.5 -11:09:41 1.0 26.65 168 Denebola 11:49:02.7 +14:34:16 2.1 14.28 154 5Bet Vir 11:50:43.0 +01:45:46 3.6 1.58 164 PPM 178587 11:45:01.3 -00:31:07 7.6 1.16 164 PPM 158193 11:46:31.8 +00:21:18 9.7 0.46 164 PPM 158210 11:47:18.7 +00:06:14 10.3 0.32 165 4138_Kalchas 11:48:20.1 +00:17:44 15.6 165 Positions are for J2000