Moon is the closest celestial object to the Earth as it is 384,400 km (238,828 miles) far from the Earth. Because of its distance, the Moon has been affecting the life in the Earth. The Moon’s presence helps stabilize the planet’s wobble, which helps stabilize the climate. It also causes tides, creating a rhythm that has guided humans for thousands of years. The Moon has many functions that hasn’t been explored further, the Moon might be used to determine the true north. In determining the Qibla direction, the calculation of the direction is by using the nearest path through the great circle. If there are three great circles on the surface of a sphere intersect each other, it will create a spherical triangle. the three points formed are the angles A, B, and C. the angle A is used to mark a certain location that needs to be determined the direction of the Qibla, angle B represents the Kaaba, while the C angle represents the North pole position or the true north. There are some methods of determining true north. There are observing of the pole star, using theodolite, using compass, and using the gnomon to cast shadow when the Sun is culminating. Since the Moon is bright enough to make objects on Earth cast shadows, it is possible to shift the method of the Sun’s culmination to the Moon to determine the true north.
This research aims to find the implementation of using the Moon’s culmination to determine the true north. The result is to find whether this method can be used as a reference for determining true north or not and how accurate is it then the result can be applied in determining the Qibla direction. This research is the qualitative research and is a field research. Primary data is taken from direct observations and calculation data of true north direction using culmination of the Moon. While the secondary data from library research sourced from journals, books about the Moon and the Qibla direction, paper, and GPS. This research is used two methods of collecting data; field observation and documentation.
This research found that the method in determining true north using the Moon’s culmination is the same as the method using the Sun’s. The difference is that the Moon’s culmination method uses the Moon when it is transiting in the meridian as the main reference. There are two formulas in determining the Moon’s culmination time. the first is by transforming the Moon upper mer. pass. data provided in the Nautical Almanac to the local time. the second is by manual calculation using the ephemeris data. The calculation and the observation show that the observation of Moon’s culmination can be conducted at the Moon age 10 until 20 or when the Moon stars to enter the gibbous phase. Meanwhile, the best time is when the Moon is in the full Moon phase and a day before and after full Moon. And after the observation, the result shows that the Moon’s culmination method has slight deviation with the Sun’s method and shows the Moon's culmination method can be used as a reference for determining the true north and applied to determine the Qibla direction or for other observation related to ‘Ilm Falak or Astronomy discussion.