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Monday, September 11, 2017

 

Daytime Occultation of Venus by the Moon (18 September, 2017)

The Moon at 09:48 am ACST in Adelaide on Monday 18 September just before the Moon covers Venus. The inset shows the Moon an Venus at this time. (click to embiggen).

WARNING! This daytime occultation occurs close to the Sun and should be attempted by experienced observers only. The Moon will be just 28 degrees (under 5 hand-spans)from the Sun. Exposure to the Sun through a telescope eye-piece can result in instant blindness. Any observation should be carried out with the sun blocked from view by a building or similar large, obscuring object with no possibility of the sun being accidentally observed.

On the morning of Monday 18 September Venus is occulted by the thin crescent Moon as seen from the most of Australia, Indonesia, Papua new Guinea  and New Zealand. The Moon is a signpost for where to look (it may be hard to see the thin moon in daylight) and Venus should be sufficiently bright to be seen near the Moon even in daylight.

Start watching about half an hour before hand to get set up and familiar with the sky. This is a daytime occultation requiring a small telescope or binoculars and extreme caution and attention to Sun safety.

Venus will appear to "wink out" as it goes behind the bright limb of the Moon, reappearance will be harder to see as you have to be looking just at the right moment.

The occultation occurs in the early morning with the Moon reasonably high above the northern horizon. The Moon is three days before new and you may need binoculars to find it, hence the need for extreme care with the sun. The Moon is also a ready signpost to Venus (although you may see Venus before the Moon). It is advisable to set up and practise on the Moon in the morning twilight before the event, so you are familiar with your telescope set-up. Set up at least half an hour ahead of time so that you can be sure everything is working well and you can watch the entire event comfortably (trying to focus your telescope moments before the occultation will cause a lot of unnecessary stress). Venus will be clearly visible in a telescope or binoculars near the Moon. Again, the Sun will be close by, so only experienced observers who can block out the Sun should attempt this.

PlaceDisappears Bright Limb Reappears Dark Limb
Adelaide ACST09:58 11:15
Brisbane AEST10:4712:20
Canberra AEST10:4712:12
Darwin ACST08:5810:41
Hobart AEST10:57 11:58
Melbourne AEST10:44 12:00
Perth AWST07:4108:33
Sydney AEST10:49 12:17

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