We recall to the visitor our methodology for calculating the beginning of the month for determining the calendar for Makkah.
After the new moon is born, we first look for the earliest crescent in the evening sky of Makkah. If it is visible, then the new month starts the next day. If not, we look further and further west until the time of fajr in Makkah. If the crescent is visible anywhere to the west before fajr in Makkah, then the new month starts on the next day, exactly as if the crescent had been visible in the evening in Makkah itself. We call this concept that of extended visibility.
The methodology for calculating the beginning of the month in Makkah can be applied to any place on earth. The month will begin next day if: (1) the new moon is born (2) if the young crescent is visible in the evening sky of the place considered, or (3) if it is visible at somewhere to the west of the place before fajr there. Otherwise the month will last a day longer.
We follow this methodology in order to determine the beginning of important Islamic dates for the various countries of the world. For several strategically chosen countries on different continents we choose a town towards the eastern limit of the country. We choose the eastern limit because fajr in the east is earlier than fajr in the west. If visibility is acquired for the east, then it will also be acquired for the west where fajr is even later. We avoid situations where there is visibility for the west but not for the east, because in such cases, the country will be divided into two for celebrating the feast day. For most countries, such a situation will not be acceptable.
The visibility curves
We now invite the reader to consult the visibility curves for the beginning of Shawwal 1433 (Eid Al Fitr 2012 / Aid el Fitr 2012). Two visibility curves are pertinent: that of 17th August 2012 and that of 18th August 2012 . The new moon is born on 17th August 2012 at 15 hours 56 minutes Universal Coordinated Time (UTC). The blue and green zones represent the areas of the world where the crescent can be seen with the naked eye, blue under good atmospheric conditions, green representing easy visibility.
The visibility curve for 17th August 2012 shows the whole earth in a non visibility zone. There will neither be direct sighting in any country nor extended visibility to the west of the country, before fajr in the country. Thus no country can celebrate Eid Al Fitr 2012 [Aid el Fitr 2012] on 18th August. 18th August will be a day of fasting.
Let us now judge the situation next day, on the evening of 18th August 2012. The green zone covers all of South America and Central America and extends towards the south of Africa and of Madagascar. The blue zone covers the southern part of the United States, the central part of Africa and extends up to western Australia. Thus, because of either direct visibility, or extended visibility to the west of the country before fajr , we have to examine whether different countries can celebrate Eid Al Fitr 1433 [Aid el Fitr 1433] on 19th August 2012.
Two considerations apply and we refer the reader to our introduction and to our country list for the beginning of Ramadan 1433 . All of south, central and northern America plus some countries in western Africa had started Ramadan on 20th July 2012 because of extended visibility in French Polynesia. These countries will have finished 30 days of fasting on 18th August 2012 and should celebrate the 1st of Shawwal, Eid Al Fitr 1433 [Aid el Fitr 2012], on 19th August 2012. For the other countries we have to see whether there is either direct visibility on the evening of 18th August or extended visibility to the west before fajr on 19th August morning. For extended visibility the choice of the reference points to which we will refer fajr in the country becomes important.
The choice of the reference points
For extended visibility, a look at the visibility map of the young crescent on 18th August 2012 leads us to the choice of two cities for referring the time of fajr in the country for which we want to determine the end of Ramadan 2012.
(1) For countries towards the east : Russia, China, Indonesia, the Indian sub-continent…, the reference point can be in the south of Madagascar, in Fort Dauphin. For all countries to the east of Fort Dauphin, fajr in the country (on 19th August morning) can be referred to the visibility time in this town on 18th August evening.
(2) For countries to the west of Fort Dauphin : Saudi Arabia, western Europe, northern Africa…, the reference point can be in Recife in Brazil.
It might be pointed out that both Fort Dauphin and Recife are in the green visibility zone and – weather conditions permitting – the photography of the young crescent should be easy. The success of our Makkah calendar is based on the large collection of photographs we have been able to obtain – thanks to reputed groups of local astronomers – as per the predictions of the visibility curves. We refer the reader to consult our photo gallery.
The best time of visibility for the new crescent : the situation in Fort Dauphin and Recife
In his paper “A Method for predicting the first sighting of the New Crescent Moon”, the British astronomer B. D. Yallop gives the following formula for determining the best time for sighting the new moon after sunset in a given place (HM Nautical Almanac Office NAO, NAO Technical Note, Updated April 1998) :
Best time of visibility of the new moon = Sunset time + 4/9 * (Difference between sunset and moonset time)
Applying the above formula we obtain:
(1) For Fort Dauphin on 18th August evening in UTC : Sunset 14H35M Moonset 15H28M (for reference : local time is UTC + 3 hours), Difference between the two 53 minutes. Best time of visibility of the new moon : 14H59M.
(2) For Recife : Sunset 20H19M Moonset 21H12M (for reference : local time is UTC – 3 hours), Difference between the two 53 minutes. Best time of visibility of the new moon : 20H43M.
source : Makkah Calendar