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2022 Jan 21 - (212) Medea - a long-duration asteroidal occultation

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A R Pratt's picture
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2022 Jan 21 - (212) Medea - a long-duration asteroidal occultation

Most asteroidal occultations are brief events, less than 10 seconds' duration, so it's rare to have one last almost a minute. Medea's 145 km-wide shadow track will sweep down England and Wales

(212) Medea / UCAC4 581-011811 event on 2022 Jan 21, 20:35 UT (asteroidoccultation.com)

It takes place around 20:15 UT on Jan 21, a Friday evening with the target star high up in Taurus just a few degrees north of the Hyades. The magnitude drop will be 0.9 m and at the moment Meda's sky motion is almost zero, producing a maximum occultation duration of 58.6 s.

A number of the UK's experienced occultation observers will be recording this event and it would be most useful to add more stations to the 'net'. (On 2011 Jan 8 observers in Japan timed 23 chords across Medea, obtaining high-quality astrometry of its position and deriving its shape profile).

The target star is mag 12.4, which is faint for visual observers, but the event could be recorded using digital imaging cameras. Computer clocks should be synchronised with a reliable UTC time source, although small timing uncertainties are acceptable for such a lengthy occultation event.  Avoid saturating the target star and use the shortest exposure setting that still gives a S/N ratio of 3 or more. 

Observing asteroid occultations with digital cameras | British Astronomical Association (britastro.org)

Tim Haymes reminds me that this event is highlighted on pages 54 and 55 of the 2022 BAA Handbook. We can help observers to analyse their recordings of the occultation.

Clear skies,

Alex.

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Any Satellites?

Thanks Alex for the reminder.  Im looking forward to monitoring this long event. I am in the shadow and it could be one of the longest durations. We will see.  My PB is a 29 second event.  There is also the slim possibility of detecting a moon. The more observers there are, the better we can probe the space around Medea.
Good luck.

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SHADOW TRACK

Hi Alex,

Is the shadow track well established. I see that I will be outside the track at Tarbatness. Is it still worth while me observing this event?

Denis

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Shadow track

Hi Denis,

The track is generally well established, although the observed track is often displaced some km from the predicted track. There's small uncertainties in the asteroid's orbit and the star's position is well defined. More event details and an interactive ground track map are available in Occult Watcher Cloud

https://cloud.occultwatcher.net/event/385-212-63655-649640-U011811

Click on the world map, drag and zoom in to Tarbat Ness. Click at your location on the map and you'll see your event mid-time is 20:13:20 UT, although your site is quite distant from the predicted shadow track (blue lines) and 1-sigma band (red lines).

It's worthwhile observing because Tim mentioned the importance of probing the space around Medea. Some asteroids have satellite moons and have been discovered by occultation observations. I suggest recording for 5 minutes centred on the mid-time.

Clear skies,

Alex.