MUHAMMADIYAH.OR.ID, YOGYAKARTA—The astronomical concept of “Imkanu Rukyat” plays a pivotal role in predicting the visibility of the crescent moon, commonly referred to as “visibility” in English. This term is particularly significant in the context of the Islamic calendar, aiding in anticipating the sighting of the hilal (crescent moon), especially during important events like Ramadan.
In the national seminar on the unified global hijri calendar on Friday (January 5), Syamsul Anwar, Chairman of Muhammadiyah, shed light on how Imkanu Rukyat operates as a form of calculation rather than direct visual observation. While traditional rukyat involves physically sighting the hilal with the naked eye or optical instruments like telescopes, Imkanu Rukyat relies on geometric positions and calculations.
One crucial divergence between Imkanu Rukyat and traditional rukyat lies in their implications for the global Islamic calendar. Both grapple with challenges related to Earth’s curvature, akin to the constraints faced when physically observing the hilal.
However, the prognostic nature of Imkanu Rukyat enables forecasting rukyat occurrences well in advance of the actual sighting day, irrespective of late-afternoon weather conditions. This sets it apart from traditional rukyat, which is significantly influenced by weather conditions such as cloudy skies or rainfall.
Another noteworthy distinction is that Imkanu Rukyat has the capacity to predict the entire Earth’s surface that will witness the hilal, unlike physical rukyat, which cannot be conducted globally due to observational limitations across different regions.
Imkanu Rukyat Transfer
Imkanu Rukyat for the first day of the crescent moon’s appearance will never encompass the entire Earth’s region. Only a small fraction of the Earth’s surface will experience Imkanu Rukyat, and this can vary from extensive to narrow regions. A similar phenomenon occurs in physical rukyat, where it is impractical for the entire Earth’s surface on the first day of rukyat to witness the hilal. Only a small portion of the Earth’s surface, which may be extensive or narrow, has the opportunity to physically witness the hilal.
The moon’s movement, progressing from east to west with an increasing elevation, impacts the likelihood of seeing the hilal. As the moon crosses eastern regions, its position may still be low, possibly even below the horizon when the sun sets. However, in western regions on Earth, the moon will be higher, presenting a better chance of sighting the hilal on the first day of its appearance.
Consequently, individuals in the west have a greater likelihood of observing the hilal on its first day of appearance. Conversely, those in far-eastern regions of the Earth, such as New Zealand, Samoa, Japan, and surrounding areas, are considered less fortunate in this regard. On the other hand, people in the Americas are regarded as more fortunate due to a higher likelihood of witnessing the hilal on its first day of appearance.
In a global context, Syaikhi Zadah, a Hanafi scholar of the later period, emphasizes that if the hilal is visible in a specific region, the rukyat applies to all humans without considering differences in matlak (absolute place). In other words, if someone in the west observes the hilal, that rukyat is considered valid for people in the east. A similar perspective is found in the views of Imam an-Nawawi, who states that some scholars in the Shafi’i school argue that rukyat in one place applies to the entire Earth’s population.
Syamsul noted that the views of the scholars refer to Imkanu Rukyat (prediction) rather than physical rukyat. This is because physical rukyat cannot be applied globally. For instance, if the hilal is seen in New York at 6:00 pm local time, in the western part of Indonesia, it is already 6:00 am. Therefore, Indonesians cannot wait for the results of physical rukyat in New York.
The statements of the scholars should be understood as “predicted rukyat,” indicating rukyat estimated based on hisab or Imkanu Rukyat. This interpretation aligns with the hadith of the Prophet Muhammad, instructing fasting and celebrating Eid al-Fitr when rukyat occurs. The hadith generally directs fasting and celebrating Eid al-Fitr when someone sees the hilal, leading to the scholars’ conclusion that wherever the hilal is visible, all Muslims must fast, including those in areas that have not seen the hilal, either because of its low position or because it is below the horizon. This perspective is suitable for formulating a global Islamic calendar.
