[This is the web version of the paper from 2007, reproduced with permission - edited by Qamar Uddin]
Alhamdulillaah. WaSalaatu WasSalaamu Ala Rasoolillaah.
Aooothobillaahi MinasShaytaanirRajeem. BismillaahIrRahmaanIrRaheem.
RabbishRahli Sadri Wa Yassirli Amri WahlulUqdatan Millisaani Yafqahoo Qauli.
This paper investigates different options proposed for determination of Islamic dates including: Global vs. Local sighting; Sighting vs. Calculations; Calculations for Dark Astronomical New Moon vs. Calculations for Visible Crescent (Hilal); Telescopes vs. Naked eye; Saudi sighting process and its implications; Issue of Eid ul Adha date; Group vs. Solo sighting ; Number of witnesses required, Size of Matla etc. Based on discussions with Scholars and Astronomers world wide, including Saudi Arabia simple solution is promoted in harmony with both Shariah and Science Insha’Allaah. May Allaah (سبحانه و تعالى) forgive, guide and help us all. Aameen.
2. Basic Information
2.1 Hilal is typically a day (or more) after the Astronomical New Moon (No Moon)
The Qur’aan states in Surah YaaSeen (translation): "And the Moon, We have measured for her mansions (to traverse)till she returns like the old (and withered) lower part of a date-stalk".
As the Moon revolves around the Earth, the light of the Sun reflected off the Moon reaching the Earth is seen as Phases of the moon. As shown in Figure 1 [above], when the Earth, Moon and Sun are roughly in a Straight line, it is the instant of “Conjunction” or the “Astronomical New Moon”. This is completely Dark / Invisible / “no-moon”. This is not the Hilaal. When the moon moves further, the reflected sunlight appears as the Crescent shape Hilal.
Also, the Astronomical New Moon (No moon) or Conjunction corresponds to the Eclipse. Despite more than one eclipses occurring during the time of the Prophet (ﷺ), no evidence exists that the Prophet (ﷺ) asked the Sahaba to start the next month based on the 'eclipse'. Thus arguments of those who want to start the month a day or two early based on Conjunction or the completely dark Astronomical New Moon (No moon) are a misguided innovation, which changes the dates.
As the Moon moves along further, it appears to lag behind the apparent motion of the Sun, thus causing the Moonset to be become later and later compared to Sunset as apparently referred in the next verse of Surah Yaseen: It is not permitted to the Sun to catch up the Moon, nor can the Night outstrip the Day: Each (just) swims along in (its own) orbit (according to Law). [Quran 36:40]
Eventually the Moon reaches the other side of the Earth (opposite to the Sun) thus showing as a “Full-moon”. If we were to start the Islamic month with the Astronomical New Moon (No moon), this Full-moon would be close to the 14th, 15th, and 16th of the month. But since the Islamic month starts with the visible crescent Hilal, which is typically ad day later, the Full-moon phases correspond to 13th, 14th and 15th month, which are reported in the Hadith as “Siyam Abyad” or “White Fasts”. This is another Daleel (proof) that the Islamic New Month starts with visible Hilaal and not with the Astronomical New Moon. The Qur’an talks about the visible Hilaal with the characteristic shape and NOT “Qamar Jadeed” nor “New Moon” nor “Iqtiran/Mahaq” (Conjunction) nor “Wiladatul-Qamar” (Birth of Moon). As the moon moves further, the shape stars waning, until we see the “reverse crescent” at Fajr. Then it disappears completely, typically for two [and half] days until it reappears as the Hilaal and the cycle repeats.