Supermoon

Tonight (Saturday 12 July) is a Super Moon.

A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth. The technical name is the perigee-syzygy of the Earth-Moon-Sun system.

The most recent occurrence was on 30 January 2014. The next occurrence will be on July 12, 2014. The closest supermoon of 2014 will be on August 10.

The Moon's distance varies each month between 222,000 miles and 252,000 miles due to its elliptical orbit around the Earth. According to NASA, a full moon at perigee is up to 14% larger and 30% brighter than one at its farthest point, or apogee.

The full moon cycle is the period between alignments of the lunar perigee with the sun and the earth, which is about 13.9443 synodic months (about 411.8 days). Thus approximately every 14th full moon will be a supermoon. However, halfway through the cycle the full moon will be close to apogee, and the new moons immediately before and after can be supermoons. Thus there may be as many as three supermoons per full moon cycle.

Since 13.9443 differs from 14 by very close to 1⁄18, the supermoons themselves will vary with a period of about 18 full moon cycles (about 251 synodic months or 20.3 years). Thus for about a decade the largest supermoons will be full, and for the next decade the largest supermoons will be new.

Reading up on it, the Supermoon was at it's best at 12.25am over the UK, which is when this photograph was taken. If I understand it correctly, the moon will be closest to Earth tomorrow (13 July) at 222,687 miles at 01.48

Set your alarm!

(For those interested I used my Olympus EM1 on a tripod, ISO 250 with Olympus 300mm (600mm FF equivalent) set at x2 digital zoom, which equates to 1200mm. F11 at 1/100 sec)