The structure has multiple usages. It is used from inside; when the sun is up the play of light on the worked surfaces. On the outside it casts shadows upon itself.
At night the moon does a similar thing and the stars are observed through the north and south 'windows'. From the north the tiny gap between the cap and its supports gives a slot which the stars transit. From a distance the quoit is skylined and therefore eclipses the rising sun. The hole in the capstone is used for direct observation of the sun when it is high in the sky, with the naked eye, and virtual apertures exist that allow the sun to be observed when it is sinking. The Solar Corona can be easily discerned. The physics of these techniques are on display at Newgrange but have not been properly explained or understood until now.
It is too complicated to go into here but I would be glad to send anyone a full explanation. Thanks for your interest. Its clearly not going to stop here.

David Kane.