The National Moon Sighting Committee will sit on Tuesday to ascertain the commencement of holy Ramadan, the lunar month of self-purification through fasting and abstinence.   The meeting will be held at the conference room of the Islamic Foundation's Baitul Mukarram office in the capital around 6:45 pm after Maghrib prayers.   State Minister for Religious Affairs Faridul Haque will preside over the meeting.   Also read: National Moon Sighting Committee meets Saturday    People, if they see the moon anywhere in the country, have been requested to inform the committee by dialling telephone numbers 9559493, 9555947, 9556407 and 9558337 or faxing - 9563397 and 9555951.   Also read: National Moon Sighting Committee to sit Tuesday