'It's all in the mix' - might be the modern idiom. Laying stones is an art - intuitive and following an indefinite plan of least resistance. Statistics is different. Thanks for the one degree correction. I know it'll be in Thom but didn't want to wade through the heriotoglyphs again. Practically it means that this daft observatory I've found in Northumberland - utterly fragile - is intended for the maximum northern moonrise, rather than the summer sun. That explains how come it's in a very remote location and is simple and small. Thanks!