Penentuan awal bulan yang akurat, dan tidak menyulitkan sangat diperlukan. Sementara, al-Quran sebagai sumber hukum utama hanya memberikan isyarat peredaran bulan, isyarat yang lebih applicable sebenarnya ditemukan dalam petunjuk Rasulullah saw, namun dipahami secara debatable oleh umat Islam. Salah satu metode penentuan awal bulan relatif moderat yang ditawarkan umat Islam adalah imkān ar-ru’yah. Para astronom, juga cenderung pada imkān ar-ru’yah dalam menentukan awal bulan Hijriah. Pada sisi lain, belum terdapat kriteria imkān ar-ru’yah yang bisa menyatukan umat Islam, sehingga terkadang muncul klaim hilal syar’i dan hilal astronomi. Karena itu, ulama menghendaki kriteria imkān ar-ru’yah selalu dikaji ulang dengan penelitian ilmiah-sistematis. Disisi lain juga, ketebalan atmosfer di Indonesia (ekuator) berbeda dengan negara lain, sehingga secara spesifik kriteria imkān ar-ru’yah Indonesia dimungkinkan berbeda dengan negara lain yang jauh dari ekuator. Berdasarkan latarbelakang tersebut penulis tertarik meneliti imkān ar-ru’yah di Indonesia dalam perspektif fiqih dan astronomi, dengan tujuan penelitian antara lain: 1). Mendeskripsikan imkān ar-ru’yah dalam perspektif fiqih, 2). Memformulasikan kriteria imkān ar-ru’yah dalam perspektif astronomi, dan 3. Menganalisis konvergensi kriteria imkān ar-ru’yah di Indonesia.
Penelitian ini menggunakan pendekatan science cum doctrinaire. Tujuan penelitian pertama, sumber datanya adalah kitab-kitab fiqih dan kitab-kitab falak yang disusun oleh ulama fiqih. Data primernya mengenai parameter dan kriteria imkān ar-ru’yah menurut ulama fiqih. Tujuan penelitian kedua, Sumber datanya adalah dokumen-dokumen Kementerian Agama RI, dan organisasi sosial kemasyarakatan. Data primernya mengenai hasil-hasil rukyatulhilal di Indonesia. Sementara tujuan penelitian ketiga merupakan analisis perpaduan antara tujuan penelitian pertama dan kedua.
Hasil penelitian menemukan: Pertama, dalam perspektif fiqih terdapat beberapa variabel yang terkait dengan imkān ar-ru’yah, yakni hisab, ufuk, hilal dan kesaksiannya, dan kriterianya. Dalam perspektif fiqih kriteria imkān ar-ru’yah disimpulkan altitude >2˚ dan elongasi >3,6˚. Kedua, dilihat dari perspektif astronomi ditemukan kriteria imkān ar-ru’yah dengan formulasi, altitude >3,7˚ dan elongasi > 5,5˚. Ketinggian bulan (altitude) dalam kriteria ini akan berubah sesuai dengan jarak beda azimut bulan-matahari. Ketiga, kriteria imkān ar-ru’yah dalam implementasinya di Indonesia menunjukkan bahwa penentuan awal bulan Hijriah di Indonesia dengan rukyatulhilal yang dapat diterima secara fiqih dan astronomi secara bersamaan sebanyak 53,41%. Kecenderungan konvergensi kriteria hilal yang dapat diterima secara astronomi dan fiqih adalah pada altitude > 2,7˚ dan elongasi >5,5˚.

ABSTRACT

The accurate determination of the beginning of month is really required. However, al-Quran as the main source of Islamic laws just provides the signals of moon circles. The applicable signals might be found in the hadis although they are still debatable among Muslims. One moderate method to determine the beginning of the month is imkān ar-ru'yah. Most astronomers tend to choose imkān ar-ru'yah to decide the beginning of new month of Islamic calender (hijriyah). On the other hand, there is no agreed imkān ar-ru'yah criteria among Muslims resulting in the claims of syar'i crescent and astronomy crescent. Therefore, many Muslim scholars suggest that imkān ar-ru'yah criteria should be developed using a systematic scientific research. In addition, the atmosphere thickness in Indonesia (the equator) is not similar to other countries so that the specific imkān ar-ru'yah criteria in Indonesia is possible to be different from other countries which are far from the equator. Based on the background, the writer is interested in to do research on imkān ar-ru'yah in Indonesia in the perspective of fiqh and astronomy. The aims of the study are: 1) to describe the imkān ar-ru'yah in fiqh perspective, 2) to formulate criteria for imkān ar-ru'yah the astronomical perspective, and 3) to analyze the implementation of the imkān ar-ru'yah criteria in Indonesia.
This research uses science cum doctrinaire approach. To reach the first research goal, the data sources are various books of fiqh and astronomy written by fiqh scholars. The primary data are the circulation and determination of early month as well as the data on the parameters and imkān ar-ru'yah criteria proposed by scholars. For the second research goal, the data sources are documents from the Ministry of Religious Affairs and social organizations. The primary data are about the results of rukyatulhilal in Indonesia. Finally, the third research objective is the analysis of the first and second research objectives.
The findings of this research are as follows. First, in the fiqh perspective, there are several variables of imkān ar-ru'yah: calculating (hisab), horizon (ufuk), crescent (hilal) and testimony, and criteria. Muslim scholars tend to differ when discussing these issues. The criteria associated with imkān ar-ru'yah in fiqh perspective is altitude >2˚ and elongation >3,6˚. Second, in the astronomy perspective, imkān ar-ru'yah criteria is formulated by altitudes >3,7˚ and elongation >5,5˚. The altitude of the moon in these criteria will change depending on the distance of the moon-sun azimuth. Third, the implementation of imkān ar-ru'yah criteria in Indonesia shows that the determination of beginning of Hijri month in Indonesia with rukyatulhilal is acceptable in both perspectives of fiqh and astronomy by 53,41%. The tendency of the new moon criteria that is acceptable in the astronomy and fiqh perspectives is altitude >2,7˚ and elongation > 5,5˚.