Dioptra
- http://members.tripod.com/Bluestar_4/Dioptra.html
- The earliest dioptra (c.300 BCE) was a device for measuring the angle, in parts of a "Sign", between two celestial objects. Photos and descriptions of how to make one and how they work.
How the Shaman Stole the Moon
- http://www.williamcalvin.com/bk6/
- An archaeoastronomy book by William H. Calvin of the University of Washington. The book, which describes a dozen ways of predicting eclipses, can be purchased or downloaded for personal reading at no charge.
Stones of Wonder
- http://www.stonesofwonder.com/
- A guide the megalithic monuments of Scotland and their astronomical alignments. Also contains illustrations, a bibliography and suggestions for the best times of year to visit.