From the sea – The moon is a celestial body orbiting the Earth. Because the source of the Moon’s visible light from Earth is the reflection of sunlight, the shape of the Moon seen from Earth will vary.
The changes in the shape of the Moon that are visible from Earth are called the phases of the Moon. Of the various phases of the Moon, there are four main phases, namely the new moon phase, the early half-full phase (first quarter), the full moon phase, and the late half-full phase (late quarter).
The period of revolution of the Moon in its orbital plane is calculated from the position of the new moon phase to the early half full phase to the full moon phase to the late half full moon phase and back to the new moon phase.
This is known as the synodic period. On average, it took 29.53059 days (29 days 12 hours 44 minutes 03 seconds).
The shape of the Moon’s orbit when the Moon revolves around the Earth is an ellipse. As a result, at some point the Moon will be at its closest position to Earth, which is known as perigee.
At other times will be at a position farthest from Earth, which is known as apoge.
The period of revolution of the Moon in its orbital plane is calculated from the position of perige to apoge and back to perige is called the anomaly period, which on average takes 27.55455 days (27 days 13 hours 18 minutes 33 seconds).
Because the length of time taken by the Moon to complete the two periods is different, at some point the Moon will be in the new moon phase and its position at the apogee.
While at other times the Moon will be in the full phase and its position in perigee. Likewise, the opposite can happen.
This can be known by comparing the time when the Moon is in a certain phase with the time when the Moon is at the perigee or apogee.
In the picture below, the Meteorology, Climatology and Geophysics Agency (BMKG) explains the timing of the phases of the Moon, the Earth-Moon distance, and the time when the Moon is at perigee and apogee in 2022.
In the picture it can be seen, the Moon at perigee and apoge is not always in the same phase.
An example is when the two positions of the Moon are closest to Earth in 2022. On July 13, 2022 at 16:07 WIB the Moon is at its closest position from Earth in 2022 with a distance of 357,263 km and 9 hours 30 minutes later the Moon is in its full phase.
Meanwhile, on December 24, 2022 at 15.32 WIB, the Moon is in perigee with a distance of 358,270 km after 22 hours 16 minutes before the Moon was in the new moon phase.
The same thing applies when the Moon is at the apogee. On June 29, 2022 at 13:08 WIB, the Moon is at the apogee as far as 406,576 km and previously at 09:52 WIB the Moon was in the new moon phase.
As described above, the effect of changing distance The Moon from Earth is the apparent size of the Moon in certain phases when at apoge and at perigee will be different.
For example, when the Moon is in its full phase on May 16, 2022, which is close to when the Moon is at perigee, the semi-diameter of the Moon as seen from Earth is 16′ 29.60″.
Meanwhile, on May 5, 2022, when the Moon’s position is at the apogee, the semi-diameter of the Moon is 14′ 44.23”.
Considering that during the new moon phase, the size of the Moon will not be observed, except during a solar eclipse, the difference between the size of the Moon during the full phase at the apogee and the Moon during the full phase at the perigee can be well observed.
Perige full moon or better known as super moon in 2022 this will occur on June 14, 2022, July 14 2022, and August 21, 2022 with the size of the Moon’s semi-diameter more than 16′ 30″.
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