A tomb AND astral observatory....are the two exclusive to one and other?....I don't know the beliefs of our forefathers(I do like to believe they had a wide enough intelligence to absorb and put patterns to the skies for their own edification and education) perhaps an afterlife was deemed accessible through the movement of the stars, maybe not...but it is a concept that has endured and been absorbed into many of today's known religions and even some extinct(known)religions. Does the application of today's knowledge prove or disprove any theories about the purpose of ancient monuments? I for one wouldn't dare to guess...just out of interest...a local radio station was asking listeners to call in with their suggestions of what they would do if they had access to the Tardis for a day...amongst the usual.."Go back to see England win the World Cup in '66" contributions...one listener actually said he would go back to see Stonehenge being erected to find out both how and why....an excellent idea IMO...though I doubt football fans would agree!
Sorry if I'm repeating another post..but theres an awful lot on this topic to try to plough through!