Occultation event with (18493) Demoleon, event index number 1693
Regions able to see the event: US,NMexico
Geocentric closest approach at 2025/12/18 02:17:03 UTC
J2000 position of star is 01:34:49.8 +10:03:48
Equinox of date position of star is 01:36:12.2 +10:11:44
Star is 141 degrees from the moon. Moon is 4% illuminated.
Stellar brightness G=15.8, apparent brightess of occulting body is G=16.2
Use an exposure time of 1.80 seconds with the standard RECON-QHY system.
SNR of 7.8 per integration for unocculted signal
Expected flux drop is 59% with SNR of 4.6 for the occulted depth (per occulted point)
Apparent velocity is 4.6 km/sec on the sky relative to the star, or, 4.9 arcsec/hr.
Position angle of asteroid motion is 9.5 degrees
The recommended exposure time corresponds to 8.2 km per image.
The 1-sigma error in the time of the event is 7.1 seconds.
The 1-sigma cross-track error in the shadow position is 3.4 km.
The sky-plane scale is 3387.1 km/arcsec.
Diameter estimates:
40.5 km assuming a 5% albedo, aximum of 8.9 sec for a central chord
16.6 km assuming a 30% albedo, maximum of 3.6 sec for a central chord
Cross-track diameter of 33.5 km used for deployment plan.
Star training set for 18493_Demoleon, (2025/12/18 02:17UT) Object RA Dec mag sep mel Aldebaran 04:37:24.8 +16:33:34 0.8 44.44 168 6Bet Ari 01:56:04.8 +20:56:02 2.6 11.75 149 102Pi Psc 01:38:28.8 +12:16:24 5.6 2.15 142 PPM 117500 01:38:41.2 +10:33:33 8.5 0.71 141 PPM 144774 01:36:38.2 +10:03:07 9.3 0.18 141 18493_Demoleon 01:36:12.2 +10:11:44 16.2 141 Positions are for equinox of date
This table contains the target star visibility for registered US sites that are relevant for this occultation. This list has been filtered to only those sites that can see the field and are within range of the shadow given the uncertainties. The observing time range has been calculated to cover the time of the event at each site with allowances for the event timing uncertainty plus time for obtaining a pre and post event baseline lightcurve. This set of stations has a 0.0 % chance of getting at least one chord. There is a 0.0% chance of 2 or more chords assuming clear weather for all.
| Site Name | Site mid-time (UT) |
Sun alt (deg) |
Sky | Moon | Star alt (deg) |
Star az (deg) |
Target | Observing Time | Xtrack (km) |
Prob |
|---|---|---|---|---|---|---|---|---|---|---|
| Patrick | 02:07:42 | -26.4 | Dark | Down | 63.1 | 155.6 | Up | 02:04:42-02:10:42 | -85.7 | 0.000 |
Star training set for 18493_Demoleon, (2025/12/18 02:17UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 44.44 168 6Bet Ari 01:54:38.6 +20:48:26 2.6 11.75 149 102Pi Psc 01:37:05.8 +12:08:31 5.6 2.15 142 PPM 117500 01:37:18.7 +10:25:40 8.5 0.71 141 PPM 144774 01:35:15.9 +09:55:11 9.3 0.18 141 18493_Demoleon 01:34:49.8 +10:03:48 16.2 141 Positions are for J2000