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Wednesday, April 02, 2014


Venus Occults the Bright Star Lambda Aquarii April 17, 2014

Venus about to cover the bright star Lambda Aquarii at 3:59 AEST on April 17 as seen from Sydney. Most other locations to see the occultation will see similar views. Telescopic view, click to embiggen.The bright star Lambda Aquarii about to exit from the dark side of Venus at 4:04 AEST as seen from Sydney. Most other locations to see the occultation will see similar views. Telescopic view, click to embiggen.
Eastern horizon from Brisbane at 3:59 AEST, 17 AprilEastern horizon from Adelaide at 3:29 AEST, 17 April

A rare occultation of a bright star by the planet Venus occurs on April 17 in Australia and New Zealand (April 16 UT). Magnitude 3.7 Lambda Aquarii will pass behind Venus starting at 17:59 UT and finishing roughly 5 minutes later at 18:04 UT. What this translates out into local times on the morning of April 17 is shown in the table below (actually there is some variation in time by up to 30 seconds or more, but you should be watching well before hand).

Venus's thick atmosphere will make this occultation different from those of the Moon, where the stars wink out almost instantaneously (unless they are skimming along some mountains). You may be able to see the star begin to peek though Venus's atmosphere before reappearing (the bright side will be too bright to see the star immerse itself in the atmosphere, unless you have some serious kit).

While in Australia the occultation takes place before astronomical twilight, in most places it is quite low to the horizon. In Adelaide it is under a handspan from the horizon, Brisbane has the best view with the occultation nearly three handspans above the horizon. So for most places you will need a fairly clear, level horizon for this occultation.

In New Zealand the occultation occurs with Venus high in the sky, but near nautical twilight.

You WILL need a telescope to see this, Venus's light will overwhelm unaided eye views, and to some degree binocular views, but anyway the really cool part is to see the star emerge from Venus's atmosphere, which you can only see with a telescope.

City Occultation Start Occultation End Height Above Horizon
Adelaide (ACST) 3:29 am 3:34 am
Alice Springs (ACST) below horizon below horizon -
Auckland (NZT) 6:01 am 6:04 am 33°
Brisbane (AEST) 3:59 am 4:04 am 16°
Cairns (AEST) 3:59 am 4:04 am
Canberra (AEST) 3:59 am 4:04 am 13°
Darwin (ACST) below horizon below horizon -
Hobart (AEST) 3:59 am 4:03 am 11°
Melbourne (AEST) 4:00 am 4:03 am 15°
Perth (AWST) below horizon below horizon -
Rockhampton (AEST) 3:59 am 4:04 am 11°
Sydney (AEST) 3:59 am 4:04 am 15°
Townsville (AEST) 3:59 am 4:04 am 10°
Christchurch (NZT) 5:59 am 6:03 am 30°

You can see some discussion in the Ice in Space forums here, with more information. A fairly impenetrable map is here.

Hat tip to Rob Kaufman  for alerting me to this occultation.

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