Friday, 4 September 2015

Lunar Eclipse September 2015 - Perigee Super Lunar Eclipse

The Total Lunar Eclipse (TLE) that will take place on the 27th of September (2015) just so happens to occur near perigee. That doesn't sound too exciting does it? How about The next TLE is a SUPER TLE! Sensational, just like the press is likely to pick up.
Super Lunar Eclipse!

So what's up with that?

The Moon's orbit about the Earth is not a perfect circle. It is an ellipse with the Earth at one of the foci points. And this ellipse is kind of wobbling so some cool mathematics are needed to keep track of these things. Here is a great web page discussing the concepts by John Walker.

So what makes up a super moon? That is simply when the Moon is full and at the point in its orbit closest to the Earth, perigee. Super moon just sounds better.

Okay, so how close to super is this eclipse coming up? Pretty close. According to world renowned calculator Jean Meeus (of Belgium) the differences are:

Moon in perigee at 01:46 UT,
mid-totality at    02:47 UT.

Within the hour! That is pretty close. And the question has been raised, just how rare is this level of Super Lunar Eclipse (SLE)?!

Darren Beard has determined that the next TLEs coming up with perigee within 15 hours of the event are not too rare,  27 Jul 2018, 21 Jan 2019. But that is within 15 hours. What about near an hour or less like this one?

Can you really tell the difference? Not unless you regularly photograph the Moon with a lens that produces an image of the Moon that fills the frame.

So cool, it is a Super Lunar Eclipse (SLE). Now let us see what the press makes of that!

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