The Turtle and the Serpent

Principles of Archaeoastronomy

as described by Dr. John Eddy and co.

Lines illustrate common sight lines used in layout of “medicine wheels” and other stone petroforms.

Eddy identified several angles which were common to most (if not all) medicine wheels and related petroforms. The shape of the wheel or petroform did not matter as long as key markers were placed at specific points on the pattern.

Diagram: Basic astronomic grid showing the markers, axes, and angles described below.


Key stones are indicated in the diagrams as: A, B, C, D, E, F, and O. Marker F is the main “back sight.”

Markers A, B, C, and D are foresights denoting the “morning star” position of specific stars. A, B and C are found in what is commonly known as the constellation Orion.

Marker O is movable and often contains submarkers for reinforcing lines A, B, C and D. However, the main purpose of marker O seems to be to set up a summer soltstice sunrise angle from Marker E.

Line E-O is relatively independent of the rest of the structure and can be slid to the outside of the form.

The stone petroforms discovered or examined under the Turtle Mountain Petroform Project usually have these markers present, but within these general rules they display considerable variety.


Each site tends to have at least a north-south axis, an east-west axis and the E-O summer soltice sunrise angle. More developed sites include A, B, C and D.

In addition, each site while more-or-less complete unto itself, also works in conjunction with other such sites. That is, one site as a point on the map may serve as its own giant marker F, while another site forms one of the sight lines. The longest distance we’ve measured so far: a solstice angle from the Turtle’s Back through the Nineteen Hills site is approximately thirty miles in length.


Angle F-A
Aldebaron morningstar, one-month after solstice approx. 63-75°
Angle F-B
Rigel morningstar, two months after solstice approx. 105-110°
Angle F-C
Sirius morningstar, three months after solstice approx. 115-116°
Angle F-D
Fomalhaut morningstar, five months after summer solstice, one month before winter solstice approx. 146°
Angle E-O
Summer solstice sunrise angle, approx. 48-52°

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