Supermoon

Nolle described the concept in a 1979 edition of Dell Horoscope including both full and new moons, but has never outlined why he chose 90% nor has provided a definitive formula for determining if a given full or new moon is "super". The basic 1979 definition read:[2]

... a new or full moon which occurs with the Moon at or near (within 90% of) its closest approach to Earth in a given orbit (perigee). In short, Earth, Moon and Sun are all in a line, with Moon in its nearest approach to Earth.

— Richard Nolle, Dell Horoscope Magazine, 1979[8]

Nolle amended his definition in 2000 specifying the distance of a given full or new moon be judged against 90% of the mean distance of perigees. Nolle (incorrectly) referenced

A SuperMoon is a perigee-syzygy, a new or full moon (syzygy) which occurs when the Moon is at 90% or greater of its mean closest approach to Earth (perigee).

— Richard Nolle, 2000, Century 21 CE SuperMoon Table[9]

NASA image showing comparison of a supermoon (left) and a micromoon (right)

In 2011, Nolle added apogees to consideration explaining that he based calculations on 90% of the difference in lunar apsis extremes for the solar year. EarthSky analyzed Nolle's tables and described the updated definition as a full or new moon is considered a supermoon if ${\displaystyle ld_{s}\leq ld_{p}+0.1*(ld_{a}-ld_{p})}$ where ${\displaystyle ld_{s}}$ is the lunar distance at syzygy, ${\displaystyle ld_{a}}$ is the lunar distance at apogee, and ${\displaystyle ld_{p}}$ is the lunar distance at perigee. Nolle based those the mean apsis extremes referencing (incorrectly) the Wikipedia article on the subject arriving at: [10][11]

any lunation closer than 368,630 km. = SuperMoon.

— Richard Nolle, 2011, Supermoon, What It Is, What It Means[11]

Nolle also added the concept of extreme supermoon in 2000 describing the concept as any new or full moons that are at "100% or greater of the mean perigee".[9]

The term perigee-syzygy or perigee full/new moon is preferred in the scientific community.[12] Perigee is the point at which the Moon is closest in its orbit to the Earth, and syzygy is when the Earth, the Moon and the Sun are aligned, which happens at every full or new moon. Astrophysicist Fred Espenak uses Nolle's definition but preferring the label of full Moon at perigee on full moons occurring "within 90% of its closest approach to Earth in a given orbit" over Nolle's calculations based on the closest of all orbits during the solar year.[13] Wood used the definition of a full or new moon occurring within 24 hours of perigee and also used the label perigee-syzygy.[7]

Sky and Telescope magazine chose a definition of 223,000 miles (358,884 km).[14]

TimeandDate.com prefers a definition of 360,000 kilometres (223,694 mi).[15]

EarthSky uses Nolle's definition comparing their calculations to tables published by Nolle in 2000.[10][9]

Wood also coined the less used term proxigee where perigee and the full or new moon are separated by 10 hours or less.[7]