18 inches; derived from distance between elbow and tip of middle finger.

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Moon rides High/runs Low

The Moon is highest above or farthest below the celestial equator.

Semidiurnal Tide

A tide with one high water and one low water every half day. East Coast tides, for example, are semidiurnal, with two highs and two lows during a tidal day of approximately 24 hours.


When the Sun crosses the celestial equator. This occurs two times each year: Vernal around March 21 and Autumnal around September 23.

Lunar eclipse

The full Moon enters the shadow of Earth, which cuts off all or part of the Moon’s light. Total: The Moon passes completely through the umbra (central dark part) of Earth’s shadow. Partial: Only part of the Moon passes through the umbra. Penumbral: The Moon passes through only the penumbra (area of partial darkness surrounding the umbra).

Growing season

Period betweenthe last killing frost in spring and first killing frost in fall.


A cloud yardstick. A ceilometer measures the height of clouds.


Fear of clouds

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