2020-07-13

Please set your alarm clock, on July 13, the moon will reach the position of the last quarter

By yqqlm yqqlm

Last Moon rises in the middle of the night, and it is easy to find it in the dawn sky.

In Kunming, it is visible in the dawn sky, rising at about 00:59 Beijing time, and reaching 64° above the southeast horizon before dawn dawns at about 06:11 and fades out of view the height of.

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In the next few days, the moon will rise later every day, so you can see less time before sunrise, and the moon is on the eastern horizon before dawn The distance above will also decrease. When the new moon comes, it rises at dawn and falls at dusk, which makes it visible only during the day.

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The moon orbits the earth every four weeks In one circle, the moon phase cycle of new moon, first quarter moon, full moon, second quarter moon, and new moon is formed every 29.5 days.

In the course of the moon going through this cycle, the observable time of the day is different. During the last quarter of the moon, the moon rises at about midnight, rises to its highest point at dawn, and falls at almost noon. Click here for more information about moon phases.

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Binoculars are used when half of the moon’s surface is illuminated The ideal time to observe the moon with a telescope or small monocular. The place where the light and dark on the moon intersect is the best place to observe the details of the moon, because along this dividing line, the moon is illuminated by sunlight from a small angle. So the long shadows cast by the mountains and craters are easy to see. At this time, if someone stands at these positions on the moon, you can see the long shadow formed by the sun on the moon’s horizon, just like what we observed when the earth is sunrise and sunset.

It is the best time to observe when the bright and dark boundary between the first and second quarters is exactly in the middle of the lunar surface.

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seasonal changes

although the moon Every month experiences a second quarter, but in different months of the year, the position of the moon in the sky before dawn is not fixed.

The moon will rise very high during the autumn equinox and much lower during the spring equinox.

This is because it always runs close to a line called the zodiac. The zodiac line marks all the planes where solar planets revolve around the sun. The zodiac passes through the zodiac constellations; and the sun sequentially passes through the zodiac signs throughout the year.

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The height of the moon that appears above the horizon at sunrise depends on The inclination of the zodiac line relative to the horizon. If the angle of the ecliptic plane to the horizon is small, the moon will rise or fall along a line that is almost parallel to the horizon, and the greater distance from the sun along this line still only corresponds to a very low altitude.

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In Kunming, the inclination of the zodiac plane relative to the horizon varies between 88° (sunrise at autumn equinox) and 41° (sunrise at equinox). On July 13, the ecliptic and the eastern dawn horizon are inclined at 71°, as shown by the yellow line in the planetarium view above, which means that in this case, the moon in Kunming is very suitable for viewing.

The position of the moon

At the moment it becomes the last quarter of the moon, the distance between the moon and the earth will reach 404,000 kilometers.

The cycle is calculated from the DE405 planet list developed by the US Space Advancement Laboratory.

This event was automatically generated by searching for a planetary calendar of interest to amateur astronomers.

Based on assumptions about the location of your location, the above text is generated.

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Related knowledge

The moon phase is the shape of the area of ​​the moon seen from the earth that is exposed to direct sunlight. The lunar phase gradually changes according to the position of the moon’s orbit around the earth and the position of the earth’s orbit around the sun during a period of a lunar month (about 29.53 days).

The rotation of the moon is locked by the gravitational tidal force of the earth, so the side facing the earth is almost always the same side. According to the position of the moon on the lunar orbit, the sunshine situation on this side is different, and the sunshine portion can vary from 0%(at the time of the new moon) to 100%(at the time of the full moon). The lunar line of the moon is the dividing line between the bright and dark hemispheres.

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each of the four”middle moon phases” is approximately It will last 7.4 days, but this number is slightly different due to the elliptical orbit of the moon. Except for some craters near the poles of the moon, such as Shoemaker, all parts of the moon will have approximately 13.77 days of sunshine, followed by 13.77 days of”night”. (The side of the moon far away from the earth is sometimes called the”dark side of the moon”, but this is a wrong statement).

Author:in-the-sky.

FY :Astronomical volunteer team

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