The calculations of astronomers and calculators regarding the crescent moon are not considered according to the established opinions of the four imams; the jurists have stated that Ramadan is not confirmed except by sighting the crescent or completing Sha'ban. Therefore, one is not obliged to follow the statements of the timekeepers, even if they are trustworthy in the authentic reports. Ibn Abidin clarified in "Tanbeeh al-Ghafil" and "Al-Wasnan" pages 98-110 with references from the books of the four schools of thought, stating: "What is relied upon and is obligatory to refer to in the opinions of the four imams is, as elaborated in the writings of their followers, that the confirmation of Ramadan can only be through sighting it at night or completing the number of Sha'ban, and that sighting it during the day is not considered, even if it is before noon according to the chosen opinion, and that one should not rely on what is reported by the people of the time and calculations and astrology." Imam Al-Laknawi authored an independent treatise titled "Al-Qawl Al-Manshur fi Hilal Khayr Al-Shuhur" emphasizing reliance on sighting, and he supports this with what was narrated from Ibn Umar, may Allah be pleased with them, who said the Messenger of Allah, peace be upon him, said: "We are an unlettered nation; we do not write or calculate. The month is like this and this and this," and he made a gesture with his thumb for the third time, "and the month is like this and this and this," meaning it can be thirty days. This is found in Sahih Muslim 2: 761, and the wording is his, and in Sahih Bukhari 2: 675. And from Ibn Umar, may Allah be pleased with them, the Prophet, peace be upon him, said: "The month is twenty-nine nights, so do not fast until you see it, and if it is obscured from you, then complete the number of thirty," in Sahih Bukhari 2: 674, and Sahih Ibn Hibban 8: 357, meaning if clouds prevent you from seeing it, you must complete the number of Sha'ban; because the original state of the month is to remain, as mentioned in Al-Qawl Al-Manshur page 148. And from Ibn Abbas, may Allah be pleased with them, the Prophet, peace be upon him, said: "Do not fast before Ramadan; fast upon its sighting and break your fast upon its sighting, and if something obstructs you from seeing it, then complete thirty days," in Jami' al-Tirmidhi 3: 72, and he said: it is good and authentic, and in Musannaf Ibn Abi Shaybah 2: 284, and the meaning of "ghiyah" is anything that obscures you, such as a cloud or otherwise, as mentioned in Al-Qawl Al-Manshur page 148. And from Abu Huraira, may Allah be pleased with him, the Prophet, peace be upon him, said: "Fast upon its sighting and break your fast upon its sighting, and if it is obscured from you, then complete the number of thirty days of Sha'ban," in Sahih Bukhari 2: 674, and Sahih Muslim 2: 674, and Al-Muntaka 1: 102. And from Hudhayfah, may Allah be pleased with him, the Prophet, peace be upon him, said: "Do not advance the month until you see the crescent, or complete the number, then fast until you see the crescent or complete the number," in Sahih Ibn Hibban 8: 238, and Jami' al-Tirmidhi 3: 68, and Sunan al-Bayhaqi al-Kabir 4: 207, and Musnad al-Shafi'i page 187. Imam Al-Laknawi said in Al-Qawl Al-Manshur page 149: "These hadiths indicate that the basis for fasting is the sighting of the crescent, and it is recommended to seek it; hence our jurists mentioned that one should not fast on the day of doubt with the intention that it is from Ramadan, because fasting it is contingent upon sighting." See also: "The Rotating Celestial Sphere in Sighting the Crescent During the Day" page 123.