Occultation event with (4138) Kalchas, event index number 936
Regions able to see the event: Australia,NZ
Geocentric closest approach at 2025/04/30 10:55:50 UTC
J2000 position of star is 09:52:01.5 +11:04:12
Equinox of date position of star is 09:53:22.9 +10:57:00
Star is 69 degrees from the moon. Moon is 10% illuminated.
Stellar brightness G=16.1, apparent brightess of occulting body is G=15.8
Use an exposure time of 2.00 seconds with the standard RECON-QHY system.
SNR of 6.6 per integration for unocculted signal
Expected flux drop is 43% with SNR of 2.8 for the occulted depth (per occulted point)
Apparent velocity is 3.9 km/sec on the sky relative to the star, or, 3.9 arcsec/hr.
Position angle of asteroid motion is 325.5 degrees
The recommended exposure time corresponds to 7.8 km per image.
The 1-sigma error in the time of the event is 10.4 seconds.
The 1-sigma cross-track error in the shadow position is 30.2 km.
The sky-plane scale is 3610.5 km/arcsec.
Diameter estimates:
55.7 km assuming a 5% albedo, aximum of 14.3 sec for a central chord
22.8 km assuming a 30% albedo, maximum of 5.8 sec for a central chord
Cross-track diameter of 55.7 km used for deployment plan.
Star training set for 4138_Kalchas, (2025/04/30 10:56UT) Object RA Dec mag sep mel Regulus 10:09:43.1 +11:50:33 1.3 4.10 72 PPM 126849 09:52:10.9 +11:43:22 6.5 0.83 68 PPM 126854 09:52:18.2 +10:45:47 7.8 0.32 69 PPM 126880 09:53:57.2 +11:10:44 11.0 0.27 69 4138_Kalchas 09:53:22.9 +10:57:00 15.8 69 Positions are for equinox of date
Star training set for 4138_Kalchas, (2025/04/30 10:56UT) Object RA Dec mag sep mel Regulus 10:08:21.9 +11:58:02 1.3 4.10 72 PPM 126849 09:50:49.2 +11:50:32 6.5 0.83 68 PPM 126854 09:50:56.8 +10:52:57 7.8 0.32 69 PPM 126880 09:52:35.8 +11:17:56 11.0 0.27 69 4138_Kalchas 09:52:01.5 +11:04:12 15.8 69 Positions are for J2000