Busy night Nov 30th - rare planetary transit and occultation

6 views
Skip to first unread message

Lukasz Wyrzykowski

unread,
Nov 18, 2025, 5:21:08 PMNov 18
to BHTOM Targets Newsletter
Dear Observers,

We would like to encourage you to take part in experimental observations for BHTOM of two new types of targets - planetary transit and stellar occultation. The main difference from most of our cases is that your observations have to be timed precisely. 

Two interesting events of this kind will happen on the very same night, Nov 30th, 2025. 

Please check the comment field below each of these to check the details on the relevant pages.

Important notes:
The star occultation by an asteroid can only be seen from a narrow band on Earth, spanning from Egypt, through Turkey, Greece, Serbia, Georgia, Hungary, Poland, Lithuania and Estonia.
To detect the occultation, please use as short an exposure time as possible and observe as densely as possible (CMOS cameras are preferred here), below 1s if possible! You also need to have perfect timekeeping (ideally from GPS) of observations stored. The total duration of the occultation is only 13 seconds!! One filter (or lack of it) is the most suitable here. The depth of the occultation is expected to be 6 mag!

The planetary transit can be observed from any Northern Hemisphere observatory. It lasts about 5h, but here the depth is only 0.05 mag! Hence, we need to have enough signal-to-noise to measure such a small excursion in the magnitude. Make sure your exposure times are long enough for this star (V~14 mag, I~13 mag). Multi-band data is of value, but if your telescope is small, it is better to invest in longer exposures and denser observations in red/IR bands. A long and very dense time series of this star is needed to cover the entire transit, together with its ingress and egress parts. 

I hope that many of you will accept this challenge. If you have prior experience in this kind of observations, please do not hesitate to take part as well! 

Clear skies!
Lukasz

Lukasz Wyrzykowski

unread,
Nov 24, 2025, 8:56:40 AM (14 days ago) Nov 24
to BHTOM Targets Newsletter
Dear All,

I wanted to remind you about the forthcoming exciting nights of the 29/30th of November and 30/1st December, when two rare events occur and we want to use them as a testbed for BHTOM. 

Asteroid occulting a star:
This is about 11 seconds disappearance of a 13 mag star visible only from a very narrow corridor on Earth. It will pass through Central Europe at around 2:30 UT. 

I encourage you to observe the event even if you are not exactly on the eclipse path. Note for this event, we need a very fast image acquisition, ideally <1 second exposure time, but long enough to see the 13 mag star. You only have 11s to catch it! Note the timing of the eclipse is not very well know!

Planetary transit:

The planetary transit should begin at around 
2025-11-30 11:00:00 UTC
and last until around
2025-11-30 17:00:00 UTC

Try catching at least part of the transit, the longer part the better, and add at least 1 h from both ends of the transit to catch the ingress and egress together with the baseline. Once you submit your data to BHTOM, we will experiment with the relative photometry to see this transit. Make sure your sampling is dense, but the key element here is the high signal-to-noise, hence make sure your exposure time is well adjusted to the magnitude of this star (about 13.6 mag in r-band). 

Clear skies!
Lukasz
on behalf of the BHTOM Team
Reply all
Reply to author
Forward
0 new messages