The Sun rises in the east. Well known fact! Will it be at the same position on every single day? To find out this, imagine that we took photographs of the position of the Sun on every day at 7:00 am from the Bekel beach, for a year and combine all these photos to a single photo. If the sun is rising in the same position for the entire year, we would have got a line. But we will have a tilted eight shaped figure with a larger lobe on one side!
The Analemma is a curve having the shape of 8 that we get by tracing the location of the sun at the same time from the same place from Earth for a year. One of its use is for estimating the position and time of sunrise and sunsets. Analemma would be different from different planets. If we do this for the moon we get a lunar analemma which is the above image.
Making lunar analemma.
With the moon, we have to take pictures with a delay of 50 minutes and 29 seconds for each day for a lunar month. Because for the moon it takes 24 hours 50 minutes and 29 seconds to reach the same position after each day. This means that if we start today at 9:00 pm we should take the photograph of tomorrow at 9:50:29 pm. Also with the moon, we would capture both, it’s the position in the sky and its phases. Astronomer Gyorgy Soponyai captured the above image from March 26 to April 18.
Why analemma is tilted 8 shaped curve with unsymmetrical lobes?
Since the moon orbits the Earth in an elliptical path, we obtain an 8 shaped curve. If the path was circular we would get a line. The orbit of the moon has a 5.15-degree tilt with that of earth, giving a tilted curve. Given the track of the moon is an ellipse, there are positions in its orbit where it is closest and farthest to earth. The farthest position, called apogee gives a larger lobe in analemma and the closest point is called perigee which accounts for the shorter lobe. Moon moves slower as it approaches apogee and it speeds up at perigee. When it moves faster its images in analemma are closer.
– Devika B S
References:
https://apod.nasa.gov/apod/ap200507.html,
Read our article on “Moon In Our Cam & The Craters We Spotted“
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