Occultation event with (17171) 99NB38, event index number 1175
Regions able to see the event: US,SMexico
Geocentric closest approach at 2025/07/31 09:42:47 UTC
J2000 position of star is 03:06:52.0 +42:46:10
Equinox of date position of star is 03:08:33.8 +42:52:00
Star is 144 degrees from the moon. Moon is 40% illuminated.
Stellar brightness G=14.2, apparent brightess of occulting body is G=16.2
Use an exposure time of 0.35 seconds with the standard RECON-QHY system.
SNR of 9.9 per integration for unocculted signal
Expected flux drop is 87% with SNR of 8.6 for the occulted depth (per occulted point)
Apparent velocity is 24.3 km/sec on the sky relative to the star, or, 22.8 arcsec/hr.
The recommended exposure time corresponds to 8.5 km per image.
The 1-sigma error in the time of the event is 1.4 seconds.
The 1-sigma cross-track error in the shadow position is 36.4 km.
The sky-plane scale is 3839.5 km/arcsec.
Diameter estimates:
46.1 km assuming a 5% albedo, aximum of 1.9 sec for a central chord
18.8 km assuming a 30% albedo, maximum of 0.8 sec for a central chord
Cross-track diameter of 46.1 km used for deployment plan.
Star training set for 17171_99NB38, (2025/07/31 09:43UT) Object RA Dec mag sep mel Aldebaran 04:37:23.5 +16:33:31 0.8 32.40 136 Algol 03:09:50.6 +41:03:08 2.1 1.83 145 PPM 045917 03:13:51.4 +42:28:14 5.9 1.05 144 PPM 045802 03:05:23.1 +42:30:54 8.3 0.68 145 PPM 045842 03:07:56.5 +43:00:19 9.3 0.18 144 17171_99NB38 03:08:33.8 +42:52:00 16.2 144 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 |
|---|---|---|---|---|---|---|---|---|---|---|
Star training set for 17171_99NB38, (2025/07/31 09:43UT) Object RA Dec mag sep mel Aldebaran 04:35:55.4 +16:30:29 0.8 32.40 136 Algol 03:08:10.1 +40:57:20 2.1 1.83 145 PPM 045917 03:12:09.5 +42:22:33 5.9 1.05 144 PPM 045802 03:03:41.9 +42:24:58 8.3 0.68 145 PPM 045842 03:06:14.6 +42:54:28 9.3 0.18 144 17171_99NB38 03:06:52.0 +42:46:10 16.2 144 Positions are for J2000