[BAA-ebulletin 00985] Rare occultation of a 5th magnitude star by an asteroid visible from UK on Sept 9/10

[BAA electronic bulletins service]

On the night of Saturday, September 9 at 23:44 UT (00:44 BST on September 
10) the asteroid (6925) Susumu (mag 17.8V) is predicted to occult star 
sigma(1) Tauri (HIP 21673, mag 5.1V). A detailed account by Alex Pratt of 
this very favourable event is available at:

https://www.britastro.org/node/11043

Given that the star is bright enough to be visible to the unaided eye, and 
that it is a spectroscopic binary star, many observers may be treated to a 
'double' shadow cast by the star system transecting the mid-UK region. The 
maximum duration of an occultation from any one location is about 2 seconds 
when the star disappears from view. Be watchful however for secondary 
events, either arising from the binary nature of the star or the distinct 
possibility that the asteroid is a binary system too. Although the marked 
uncertainty in the exact location of the track is about 100 km, given 
duplicity in the star/asteroid, observers several hundred km either side of 
the centre-line should watch for a positive occultation event. Likewise, 
start observing a few minutes ahead of the due time and continue a few 
minutes after too in order to capture unexpected phenomena. Note that the 
star is in Taurus and will be fairly low towards your eastern horizon.

Do please make every effort, weather permitting, to observe this especially 
rare event. If you are able to use a video camera hooked up to some form of 
optical aid then do consider using it, as this type of permanent record is 
invaluable observation-wise. Visual observers should also attempt to time 
the event, both the duration of the disappearance and the absolute time if 
at all possible. An easy way to add time marks to your video record (say 
after the start and before the end)is to momentarily shine a flashlight or 
similar near the entrance of your optics, synchronising the flash as 
accurately as possible to some reliable time signal.

Good luck everyone!

Richard Miles
Director, Asteroids and Remote Planets Section
2017 September 07 09:24 UT