Occultation event with (19725) 99WT4, event index number 1436
Regions able to see the event: US,RECON
Geocentric closest approach at 2025/10/31 11:33:32 UTC
J2000 position of star is 11:11:43.1 +14:23:37
Equinox of date position of star is 11:13:04.4 +14:15:10
Star is 165 degrees from the moon. Moon is 68% illuminated.
Stellar brightness G=15.8, apparent brightess of occulting body is G=16.5
Use an exposure time of 0.45 seconds with the standard RECON-QHY system.
SNR of 3.2 per integration for unocculted signal
Expected flux drop is 65% with SNR of 2.1 for the occulted depth (per occulted point)
Apparent velocity is 30.2 km/sec on the sky relative to the star, or, 27.3 arcsec/hr.
Position angle of asteroid motion is 108.4 degrees
The recommended exposure time corresponds to 13.6 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 27.5 km.
The sky-plane scale is 3983.5 km/arcsec.
Diameter estimates:
41.1 km assuming a 5% albedo, aximum of 1.4 sec for a central chord
16.8 km assuming a 30% albedo, maximum of 0.6 sec for a central chord
Cross-track diameter of 31.7 km used for deployment plan.
Star training set for 19725_99WT4, (2025/10/31 11:34UT) Object RA Dec mag sep mel Regulus 10:09:44.7 +11:50:24 1.3 15.61 179 68Del Leo 11:15:28.7 +20:22:54 2.6 6.16 163 70The Leo 11:15:35.6 +15:17:17 3.3 1.20 164 PPM 128054 11:13:04.9 +14:15:34 6.6 0.01 165 19725_99WT4 11:13:04.4 +14:15:10 16.5 165 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 16.3 % chance of getting at least one chord. There is a 14.5% 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 | 11:30:39 | -23.8 | Dark | Down | 31.6 | 94.2 | Up | 11:28:20-11:34:20 | 184.4 | 0.000 | George/Scottsdale | 11:30:30 | -28.6 | Dark | Down | 26.8 | 90.1 | Up | 11:27:56-11:33:56 | 84.0 | 0.006 | Cobble | 11:30:56 | -15.7 | AT | Down | 39.7 | 99.0 | Up | 11:28:42-11:34:42 | -37.9 | 0.155 | Hodapp | 11:30:56 | -15.3 | AT | Down | 40.1 | 99.3 | Up | 11:28:43-11:34:43 | -39.1 | 0.147 |
This table contains the target star visibility for registered RECON 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 43.3 % 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 |
|---|---|---|---|---|---|---|---|---|---|---|
| Wildwood | 11:30:22 | -34.2 | Dark | Down | 21.2 | 86.6 | Low | 11:27:44-11:33:44 | 198.2 | 0.000 | Lake Havasu City | 11:30:27 | -30.6 | Dark | Down | 24.8 | 89.1 | Low | 11:28:00-11:34:00 | 191.6 | 0.000 | Idyllwild | 11:30:24 | -32.7 | Dark | Down | 22.8 | 87.5 | Really Low | 11:27:24-11:33:24 | 136.4 | 0.000 | Calipatria | 11:30:25 | -31.7 | Dark | Down | 23.7 | 87.8 | Low | 11:27:38-11:33:38 | 56.7 | 0.052 | Yuma | 11:30:26 | -31.0 | Dark | Down | 24.5 | 88.1 | Low | 11:27:28-11:33:28 | 0.1 | 0.381 |
Star training set for 19725_99WT4, (2025/10/31 11:34UT) Object RA Dec mag sep mel Regulus 10:08:21.9 +11:58:02 1.3 15.61 179 68Del Leo 11:14:06.7 +20:31:22 2.6 6.16 163 70The Leo 11:14:14.3 +15:25:44 3.3 1.20 164 PPM 128054 11:11:43.7 +14:24:00 6.6 0.01 165 19725_99WT4 11:11:43.1 +14:23:37 16.5 165 Positions are for J2000