standstill compass
{{name}}, this is the eastern horizon. the dot is where the full moon rises at its monthly northernmost extreme — for the year and the latitude you set.
the moon's orbit is tilted 5.145° to the ecliptic, and that tilt rotates once every 18.6128 years. each monthly extreme of the moon's declination swings between about +18.3° and +28.6° over that period. at the high end — the major standstill — the full moon rises further north than at any other point in the cycle. at the low end — minor standstill — the swings are minimal.
the newark octagon in licking county, ohio (hopewell, ~100 BCE – 400 CE) has its principal axis at azimuth ≈52° — the major-standstill moonrise at 40°N. ray hively and robert horn, an astronomer and a philosopher at earlham college, published the alignment in archaeoastronomy vol. 4 in 1982. the next major standstill is autumn 2043.
stonehenge's causeway axis (51.2°N) aligns to the major-standstill moonrise at roughly 40°. clive ruggles and others have argued the 56 aubrey holes — one for each third of the 18.6-year period, approximately — served as a lunar standstill tally. callanish on lewis (58.2°N) is more extreme: at major standstill the moon barely clears the horizon and, from the right approach, appears to set into the stones. mnajdra on malta (35.9°N) and el caracol at chichén itzá (20.7°N) are framed differently — the cycle shows as a subtler azimuth range at lower latitudes, which the chart makes visible.
the math is the textbook horizon equation: cos(A) = sin(δ) / cos(φ). it ignores atmospheric refraction (~0.5°), parallax, and the observer's eye height. for hopewell-grade accuracy it is plenty.