Bandung – BRIN Public Relations. “Currently there is still a dichotomy between Rukyat and Hisab, which in fact has an equal position in astronomy,” said Thomas Djamaluddin, an astronomy expert from the National Research and Innovation Agency (BRIN), in a Seminar on Determining the Hilal – new moon -Position to mark the Beginning of Ramadan Month 1443 Hijri on the virtual channel of the Ministry of Religious Affairs, Friday (1/4).

Thomas explained that to see the hilal, optical aids in the form of a telescope are needed for observing celestial bodies. Hilal is the first crescent moon observed after maghrib – sunset, which is the mark of the beginning of a month. The hilal is the strongest evidence that the moon phase has changed, which is preceded by the old crescent and the new moon. “The Messenger of Allah only gave examples without explaining the reasons, but astronomically rukyatul hilal or moon observation is very reasonable,” said Thomas.

Determination of hisab – calculation, he revealed, has developed since the time of the Messenger of Allah, including the urfi calculation, taqribi calculation, and haqiqi calculation. “The Urfi calculation method has developed since the time of the prophet and is still used by community groups,” he explained. Furthermore, he explained the method of taqribi calculation as used in the book of Sulamunnayirain, and the haqiqi calculation with astronomical formulation which is divided into two criteria. First, the criterion is lihatul hilal (simple) and the second is the criterion is of imkan rukyat (visibility).

In his presentation, Thomas said, it is necessary to have criteria to determine the beginning of a month and that rukyat requires verification to avoid mistaken rukyat. “Hisab cannot determine the beginning of a month without any criteria,” he affirmed.

Criteria are the basis for making a calculation-based calendar that can be used in rukyat estimates. According to him, the criteria that need to be adopted include the Syar’i proposition at the beginning of a month and the results of a valid astronomical study. “The criteria must seek a common ground for rukyat practitioners and hisab practitioners to become a mutual agreement,” explained Thomas.

Peeking Hilal on the beach of Santolo Garut

Meanwhile, the Garut space and atmosphere observation and technology Test Center participated in observing the new moon on the Santolo coast of Garut to determine the start of Ramadan. These observations are also taken into account in the astronomical calculation (hisab) and the mechanism for observing the new moon (rukyatul hilal) on Friday afternoon (1/04).

Coordinator of the space and atmosphere observation and technology test Center, Unggul Satrio and his team also made preparations for the observation of the rukyatul hilal, yesterday (1/4). Observation was carried out at the Garut BRIN observation point, which was previously called the LAPAN Center for Flight Test and Atmospheric Space Observation Technology, Garut.

According to him, the current position of the moon (at 16.31 West Indonesia Time) through the skymap is already visible on the horizon. “Right now it is approaching the horizon at point 17.35 and later at sunset it will be at 17.54. The optimal point is at 17.40 to 17.56. By calculation of the title, hilal already exists, but it is still around 1.9 degrees. Under the current cloudy weather condition, it might be difficult to see the moon. But it would not be a problem if the circumstance allows it,” he said.

“This activity is one way to validate the existing calculations (estimation of the start of Ramadan). Actually, differences are not a problem. Instead, they strengthen us,” said Unggul. “These differences show that Indonesia is very rich in astronomy people who can support religious activities, such as the beginning of Ramadan, Shawwal, and later Dzulhijjah. This of course refers to the decree of the Minister of Religious Affairs,” he added

Determination of Global Islamic Calendar

To unify the global Islamic calendar, the Jakarta Recommendation 2017 (RJ2017)/ MABIMS New Criteria propose three inseparable points. Thomas explained these three points. First, the criteria to determine the beginning of a month are elongation of the moon minimum 6.4 (degrees) and a minimum height of the moon of 3 at sunset in the Southeast Asia Region. Second, the International date limit is used as the global Islamic calendar date limit. Third. The OIC (Organization of Islamic Cooperation) is the collective authority in setting the global Islamic calendar.

“Astronomers and policy makers worked systematically and gradually to be further discussed at the MABIMS level until it was finally adopted by the Minister of Religious Affairs of the Republic of Indonesia for implementation since 2022,” said Thomas. The Indonesian Minister of Religious Affairs through the Isbat Session announced that the start of Ramadan falls on Sunday (3/4).

For information, MABIMS stands for Ministers of Religious Affairs in the Southeast Asian Region including Brunei Darussalam, Indonesia, Malaysia and Singapore. The Isbat Session to determine the start of this year’s fasting month was held on Friday (1/4). In addition to determining the start of fasting, the isbat session is also carried out to determine the beginning of other Hijri calendar months, such as Eid al-Fitr to Eid al-Adha. (hmn, rte/ ed: kg, drs)