Occultation event with (17171) 99NB38, event index number 1163
Regions able to see the event: Japan
Geocentric closest approach at 2025/07/23 16:19:04 UTC
J2000 position of star is 03:01:55.4 +41:57:22
Equinox of date position of star is 03:03:36.0 +42:03:20
Star is 53 degrees from the moon. Moon is 2% illuminated.
Stellar brightness G=16.3, apparent brightess of occulting body is G=16.3
Use an exposure time of 0.75 seconds with the standard RECON-QHY system.
SNR of 3.1 per integration for unocculted signal
Expected flux drop is 50% with SNR of 1.6 for the occulted depth (per occulted point)
Apparent velocity is 26.8 km/sec on the sky relative to the star, or, 24.7 arcsec/hr.
The recommended exposure time corresponds to 20.1 km per image.
The 1-sigma error in the time of the event is 1.3 seconds.
The 1-sigma cross-track error in the shadow position is 37.1 km.
The sky-plane scale is 3908.9 km/arcsec.
Diameter estimates:
46.1 km assuming a 5% albedo, aximum of 1.7 sec for a central chord
18.8 km assuming a 30% albedo, maximum of 0.7 sec for a central chord
Cross-track diameter of 46.1 km used for deployment plan.
Star training set for 17171_99NB38, (2025/07/23 16:19UT) Object RA Dec mag sep mel Aldebaran 04:37:23.4 +16:33:31 0.8 32.45 38 Algol 03:09:50.5 +41:03:08 2.1 1.54 52 PPM 045917 03:13:51.4 +42:28:14 5.9 1.94 51 PPM 045746 03:01:58.6 +42:14:24 8.4 0.35 53 PPM 045780 03:03:55.8 +42:04:22 9.2 0.06 53 17171_99NB38 03:03:36.0 +42:03:20 16.3 53 Positions are for equinox of date
This table contains the target star visibility for registered Japan 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 14.6 % chance of getting at least one chord. There is a 3.9% 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 |
|---|---|---|---|---|---|---|---|---|---|---|
| Fukuoka | 16:17:33 | -35.0 | Dark | Down | 22.4 | 53.5 | Up | 16:14:55-16:20:55 | -59.0 | 0.129 |
| Kumamoto | 16:17:30 | -35.7 | Dark | Down | 22.1 | 53.4 | Up | 16:14:38-16:20:38 | -84.6 | 0.039 |
| Kagoshima | 16:17:26 | -36.9 | Dark | Down | 21.2 | 52.9 | Low | 16:14:29-16:20:29 | -95.7 | 0.021 |
Star training set for 17171_99NB38, (2025/07/23 16:19UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 32.45 38 Algol 03:08:10.1 +40:57:20 2.1 1.54 52 PPM 045917 03:12:09.5 +42:22:33 5.9 1.94 51 PPM 045746 03:00:18.0 +42:08:24 8.4 0.35 53 PPM 045780 03:02:15.1 +41:58:25 9.2 0.06 53 17171_99NB38 03:01:55.4 +41:57:22 16.3 53 Positions are for J2000