' The stone leans towards the north-east sector of the circle where an arrangement of stones may represent an earlier, possibly contemporary cairn or cist. That this feature also pre-dates the circle is apparent in the spacing of the circle uprights at this point. When the circle itself was erected, the quartz stone was placed on the south-west side of the circle in alignment with the central stone and the cairn-like structure to the north-east...

Anyone who cares to study an aerial view of this elliptical circle will quickly see that a central line through the quartz stone and the base of the leaning stone does not align with the 'cairn-like structure'. It does in fact run to the outside of the more eastern side of the two uprights forming the possible cist/cairn. Furthermore, because those standing stones either side of the said cist/cairn are slightly closer together than the other regular spacing's is not proven evidence that it predates the circle.

'The south-west position of the quartz stone also marks the direction of the full moon during mid-summer.'

I have no idea if that is true or not but would it be the same every year?