The March “Mini-Moon”


The Full Moon of March 5 will be the smallest and most distant Full Moon of 2015.

In recent years there’s been a huge ado about “supermoons,” the largest and closest Full Moons of the year. This year the biggest Full Moon occurs on September 27.

Photographers wishing to capture a comparison of the biggest Full Moon with the smallest will need to shoot the Moon this week, on March 5. That’s the date for 2015’s most distant and smallest Full Moon – the “mini-moon” of March.

On March 5 the Moon reaches its “apogee” – the most distant point in its monthly elliptical orbit around Earth about 10 hours before it reaches the moment of full phase at mid-day on March 5 for North America. On March 5 the Moon’s maximum distance will be 406,384 kilometres from Earth (measured from the centre of Earth to the centre of the Moon). By nightfall on March 5 the Moon will be a little closer than that but not by much.

Seven Full Moons later, on September 27, the Moon will reach its monthly “perigee” point closest to Earth less than an hour before full phase, at a distance of 356,877 kilometres. That will be the much-publicized “supermoon” of 2015.

Shoot both Full Moons with the same optical system (preferably a telescope with a focal length of at least 600mm to make the Moon large enough on the camera frame) and you’ll have a pair of real images comparing the minimum and maximum apparent sizes of the Moon, much like the simulations above.

You’ll certainly be out shooting the September 27 Full Moon, as that night it also undergoes a total eclipse. The Full Moon will turn deep red in the early evening for North America. But wait until the umbral phase is over, and you’ll have a normal looking Full Moon to create the comparison pair.

There’s also a total lunar eclipse next month, on the morning of April 4, six Full Moons before the September “supermoon” eclipse.

However, that’s not the smallest Full Moon of 2015. On April 4 the Full Moon comes three days after the Moon’s monthly apogee point, putting it a little closer than this week’s Full “mini-Moon” of March.

The difference between the two extreme Moons is only about 12 percent, between a lunar disk 30 arc minutes across (1/2 degree) at apogee and one 34 arc minutes across at perigee.

The difference is impossible to detect to the eye, not without two Moons side-by-side in the sky, something we’ll never see.

But by taking photos of the March and September moons with the same optics you can create a matched two-moon comparison.

Clear skies!

– Alan, March 1, 2015 / © 2015 Alan Dyer / www.amazingsky.com

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