Hey up,

I think you may've been a bit out on bearings for this cairn circle....
If you have a fester at this crap pic http://www.themodernantiquarian.com/post/29836 the cairn circle can just about be seen to the left of the tree....
The hole with the genny in it you show in your pic... is I reckon a wallers stone quarry...

nice one
stu.