How many years does a total lunar eclipse occur?

“A total lunar eclipse occurs once every fourteen months, but it may not be visible. Lunar eclipses generally occur on the lunar calendar, which is the 15th or 16th day of each month in the lunar calendar. Globally, lunar eclipses Total eclipse is a common astronomical phenomenon that occurs twice every three years. The widest solar eclipse zone on the earth is no more than 300 kilometers, and the narrowest total lunar eclipse is when the moon, earth and sun are in the same straight line. A natural phenomenon in which the moon completely enters the earth's umbral shadow, as if the moon was "swallowed"."

On a global scale, lunar eclipses do not occur every year, and not every lunar eclipse occurs. It is a total lunar eclipse. According to statistics in the "Saros Cycle", approximately 28 lunar eclipses (about 43 solar eclipses) occur in a cycle of about 6585 days (a little more than 18 years), of which 12 to 13 are lunar eclipses. Whole foods. Simply put, a total lunar eclipse occurs approximately once every year and a half. It should be noted that every time a lunar eclipse occurs, only people in half of the earth (night hemisphere) can see it. Therefore, in order to see a total lunar eclipse in the same area, it takes an average of three years, and the total lunar eclipse occurs when is not fixed. Lunar eclipses can be divided into three types: partial lunar eclipse, total lunar eclipse and penumbral lunar eclipse. Total lunar eclipse is relatively rare.

The process of a total lunar eclipse is divided into five stages: initial waning, complete eclipse, extreme eclipse, light generation, and full circle.

First waning: The moon has just touched the Earth's umbral shadow, marking the beginning of a lunar eclipse.

Eclipse: The western edge of the moon is inscribed with the western edge of the earth's umbra, and the moon just completely enters the earth's umbra.

Eclipse: The center of the Moon is closest to the center of the Earth's umbral shadow.

Light generation: The eastern edge of the moon is inscribed with the eastern edge of the earth's umbra, and the total eclipse phase ends.

Compound circle: The western edge of the moon is extrinsic to the eastern edge of the Earth's umbral shadow. At this time, the entire lunar eclipse ends.

Principle diagram of a total lunar eclipse. For the earth, the directions of the sun and the moon are 180° different. Because the orbits of the sun and the moon in the sky, called the ecliptic and the ecliptic respectively, are not on the same plane. It is an intersection angle of about 5°, so only the sun and the moon are located near the two intersections of the ecliptic and the ecliptic, respectively, and have the opportunity to form a straight line and produce a total lunar eclipse.

The degree of eclipse of the moon is called "eclipse"

Total lunar eclipse, which is equal to the ratio of the farthest distance from the edge of the moon wheel deep into the earth's umbra to the apparent longitude of the moon at the time of the eclipse.

How to observe a total lunar eclipse: Use binoculars or an astronomical telescope, which can be clearly viewed with a magnification of 7 times or more. You can stand at a high place and have a good view. It can also be observed directly with the naked eye. Without any special equipment, you can make the following two total lunar eclipse observations.

Before the observation, prepare some observation paper. There is a large circle drawn on the paper. 0° to 360° are marked on the circle in a counterclockwise direction. The position of 0° represents the true north point of the moon. During the total lunar eclipse, draw a sketch of the lunar eclipse every 4 minutes. The result of this is a set of eclipse diagrams of the entire lunar eclipse.

Brightness and color

The brightness and color of the moon during a lunar eclipse can be divided into the following five levels: Level 0, very dim and almost invisible; Level 1, slightly brighter and black Yellow, the details of the schematic diagram of the total lunar eclipse are difficult to distinguish; level 2, slightly bright, black-red or brownish-yellow, with some dark spots in the center, and the outside is quite bright; level 3, brick red, the details of the lunar surface can be seen, but very blurry; 4 Grade, coppery red, very bright, the outside is very bright, slightly blue, and large details can be seen. When observing a total lunar eclipse, you must judge the brightness and color levels of the moon and record them. Also record the weather conditions at the time.

A "serial four-month eclipse" means that "total lunar eclipses" will occur for four consecutive months in two years, and the moon looks dark red; a rare "serial four-month eclipse" that only occurs in 500 years It happened three times, and the fourth time happened in April and October this year.

When the moon enters the umbra without direct sunlight, the atmosphere absorbs all the purple, blue, green, and yellow light, leaving only red light that can penetrate and refract to the moon's surface, forming The dark red moon, also known as the blood moon, is also a "total lunar eclipse".

A blood moon is also called a total lunar eclipse. It will occur once or twice a year, but consecutive four-month eclipses are very rare. Total lunar eclipses have occurred for four consecutive months in two years. There have been only three times in 500 years. The fourth time was on April 15 and October 8 this year.

Lunar eclipses can be divided into three types: partial lunar eclipse, total lunar eclipse and penumbral lunar eclipse. A partial lunar eclipse occurs when only part of the moon enters the earth's umbra; and a total lunar eclipse occurs when the entire moon enters the earth's umbra. As for a penumbral lunar eclipse, it means that the moon only passes through the penumbral area of ??the earth, causing a very slight decrease in the brightness of the moon, making it difficult to see the difference with the naked eye.

There is no annular lunar eclipse. Since the Earth's umbra is much larger than the Moon's, this also means that during a total lunar eclipse, the Moon will completely enter the Earth's umbral area, so there will be no annular lunar eclipse.

The lunar eclipse must occur in "Wang" (that is, around the 15th day of the lunar calendar). When the moon enters the penumbra of the earth, it should be a penumbral eclipse. However, because its brightness weakens very little and is difficult to detect, it is not called a lunar eclipse. Some people believe that there are only two types of lunar eclipses: total lunar eclipse and partial lunar eclipse.