This article discusses the use of the Hilal Remote Observatory (HRO) in determining the beginning of the Hijri month from the perspective of Islamic law. The determination of the beginning of the Hijri month has essential implications in determining Muslims’ worship and daily activities. So far, hilal observations are carried out by direct observation methods, both without tools (naked eye) and with tools (telescopes, theodolites, and so on) in rukyat places. However, with the development of technology, HRO can now be done. HRO (long-range hilal observation) is a modern technology that allows remote observation of hilal using optical devices and communication technology. With HRO, an observer can move the device remotely and view the moon from various geographical locations in real time. This article aims to answer the formulation of the problem, namely how to use HRO in determining the beginning of the Hijri month according to Islamic law. This article produces an opinion that the existence of HRO technology in rukyatul hilal can be used and utilized because it can help provide certainty and confidence about the existence of Hilal. In addition, HRO can make it easy for observers to see the moon because it can be done wherever the observer is. As for the testimony of seeing the hilal of an observer who is far from where the instrument is placed, it cannot be used as a basis to establish the beginning of the Hijri month for the place where the observer is located unless the place where the observer is located west of where the instrument is located or is in the same matla' jurisdiction with the place where the instrument is located. This is because worship is based on position and time.
Siti Tatmainul Qulub (Tue,) studied this question.