Reference: Fataawa Ramadhaan – Volume 1, Page 62, Fatwa No.28
al-Fataawa libni ‘Uthaymeen – Kitaab ad-Da’wah – Volume 1, Pages 150-151
Question: What is the legislated Sharee’ah method by which the beginning of the month is established? And is it permissible to rely on astronomical observatories in determining the beginning of the month and its ending? And is it permissible for the Muslim to use a telescope in sighting the crescent?
Response: The legislated Sharee’ah method in verifying the beginning of the month is for the people to try to sight the crescent. And [in doing so] it is befitting the sighting be verified by one who is trustworthy with respect to his religion [and character] and strong vision. So if they sight it, they must act upon this sighting, and start fasting if it was the crescent of Ramadhaan, or stop fasting if it was the crescent of Shawwaal.
It is not permissible to rely on the calculations of the atsonomical observatories if there was no actual sighting. However, if there was a sighting, even if the sighting was through the astronomical observatories, then it is accepted, since it falls under the general statement of the Prophet ﷺ:
«When you see it then fast, and when you see it break your fast»
As for calculations, then it is not permissible to act upon it, nor to rely on it.
As for the use of what is known as a telescope – which is a glass instrument that magnifies the crescent – then there is no harm in using it, however, it is not obligatory. [This is] because what is apparent from the Sunnah is the reliance upon normal sighting [with the naked eye], and not anything else. However, if it is used, and someone trustworthy sights it, then this sighting is to be acted upon.
The people of the past would use similar means when they would climb up to a height after Maghrib on the 29th day of Sha’baan or Ramadhaan; So they would seek out the crescent [from this height] using a telescope.
In any case, whenever the sighting of the crescent is verified, in whatever manner it was seen, then it is obligatory to act upon this sighting, based on the generality of the statement of the Prophet ﷺ:
«When you see it then fast, and when you see it break your fast»
