By David Bentley & Anders Anglesey Some two billion Muslims are preparing to celebrate Eid al-Fitr tomorrow and mark the end of Ramadan. Muslims pay attention to lunar cycles to help them work out when the celebrations will take place. All across the globe, Muslims have looked to the western horizon in the hope of seeing a crescent moon. Muslims traditionally look for the moon on the 29th day of Ramadan and use it to calculate when Eid al-Fitr, also known as Eid ul-Fitr, will take place. Astronomers in Saudi Arabia said they had not seen a crescent moon on April 8 and that the celebration woul…