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Partial lunar eclipse tonight
BY MARK ARMSTRONG
ASTRONOMY NOW

Posted: 18 October 2013


eclipsegraphic
The lunar eclipse on the night of 18/19 October. AN graphic by Greg Smye-Rumsby.

The second lunar eclipse of the year takes place on 18/19 October, again this is a partial penumbral eclipse when the Moon is immersed in the lesser, outer region of the Earth's shadow called the penumbra. The UK is perfectly placed for once to see the entire event with the Moon at a decent altitude too. The first eclipse back in May was virtually undetectable as only a very small portion of the Moon enter the penumbral shadow. This one is much deeper with a magnitude of .7649 (The magnitude of an eclipse is the fraction of the diameter of the eclipsed body which is in eclipse), making the effect visible to the naked eye. However its not like a partial lunar or solar eclipse where it easy to see a bite being taken out near the Iimb; in a penumbral eclipse at least two-thirds of the Moon has to be immersed in the shadow for it to be apparent, although local atmospheric conditions and how high the Moon is in the sky are important considerations.

From the UK
The eclipse starts at 10.50pm BST with the Moon 40 degree up in the south eastern sky. By just after midnight the effects of the dulling effect of the penumbra should be apparent given good local conditions but won't last that long. At the time of mid-eclipse the Moon is riding 50 degrees high and is still 45 degrees up by the time the eclipse ends at 2.50am BST.

From North America
The observing circumstances are not ideal for America but the eclipse is visible with the further north and east you are the better. From New York the Moon rises at 5.58pm EDT, 10 minutes after the eclipse starts. By the time of mid-eclipse at 8pm the Moon is 20 degrees high due east and climbs to 42 degrees in the east-south-east by the time the eclipse ends around 10pm. Heading down the east coast to Miami, at mid-eclipse the Moon is 16 degrees up and climbs rapidly to 40 degrees by eclipse end at 10pm. Heading west to Chicago the Moon rises at 5.54pm CDT and so the start of the eclipse is not visible. Mid-eclipse occurs at 6.50pm but the Moon is only 10 degrees up and the effects of the evening twilight are still a factor. However all is not lost as the Moon has climbed to 31 degrees by 9pm CDT when the eclipse ends. Houston residents will only see the last stages of the event as the Moon rises at mid-eclipse and hauls itself just short of 30 degrees by the end at 9pm. The west coast is not favoured at all; from Los Angeles the Moon will still be engulfed in the murk at the local horizon, less than 10 degrees up at the end of the eclipse at 7pm PDT.

In the Southern Hemisphere
This is eclipse is not visible Australia and New Zealand with the Moon setting as the eclipse starts. Observers in South Africa are superbly placed to see the whole eclipse; from Cape Town the event lasts from midnight to 4am. From eastern South America observers in Sao Paulo, Brazil can see the whole eclipse from 7pm to 11pm local time but at the start the Moon will be under 10 degrees up and evening twilight a factor. From Buenos Aires, Argentina the Moon will be 20 degrees up at the time of mid-eclipse at 9pm local time.

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Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
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3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
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