In astronomical terms, he says that particular partial solar eclipse will align with the galactic equator, an arbitrary line in the sky representing the midpoint of the disk-shaped Milky Way galaxy. The galactic coordinate system Harper uses in his analysis wasn’t formalized until 1958, refining (and shifting) and earlier system from 1932, itself drawing on one first proposed in 1785. The Great Pyramid was constructed around 2450 BCE, long before the current arbitrary galactic equator existed.
It’s not clear, though, that Harper distinguishes between the galactic coordinate system and a geocentric astrological coordinate system that projects the earth’s latitude and longitude out onto the celestial sphere. Thus, while he uses the scientific term “galactic equator” he appears to be referring at times to fringe claims made about the “celestial equator,” which arbitrarily projects the Earth’s equator out into the sky, particularly since he relates the coordinate system to the precession of the equinoxes, the slow change in the apparent position of the stars due to the wobble of the Earth’s axis. This axial movement changes the location of stars in the geocentric coordinate system but not the heliocentric one (though our perception of the heliocentric system will, of course, change with the movement of the Earth’s axis). This image, from here, might make it a little clearer how the two systems differ:
Using the modern 1958 coordinate system, Harper determines that the June 2020 eclipse will not be visible at Stonehenge, but that beneath the plane of the Earth, the sun will be “sitting” on the moon at dawn in both locations, at the intersection of the 1958 galactic equator and the ecliptic. At the Great Pyramid, the eclipse will take place in the sky, but it will be only a partial eclipse, so he concocts a reason for that, too: He thinks the Egyptians wanted to symbolize the balance of light and dark! “This is Stonehenge and the Great Pyramid in space. This is the only time this alignment of the earth, moon and sun happens along the galactic equator in this way!”
He concocts an elaborate geometric argument for why the Great Pyramid actually symbolizes this particular eclipse, but it boils down to drawing circles around an unexplained drawing of the pyramid, which seems to be a cross-section parallel to the faces of the pyramid—but why not a cross section from corner to corner, or the view from outside? He then squares the circle, draws more circles around the leftover bits and calls the whole thing and image of the solstice eclipse that, by his own admission, is not visible in that location in the manner so depicted. The correlation only “works” if we assume that the Great Pyramid is a scale model of the Earth, and then lop a chunk off the top to represent the moon, for which there is no evidence whatsoever on the ground or in ancient texts.
Putting this all together with Graham Hancock’s speculation in Magicians of the Gods that a comet, or fragment of one, hit the earth around 12,800 BCE and will strike again between now and 2040, he concludes that ancient monuments are warning us that in 2020 we will pass through the same debris field that spawned the earlier disaster and we therefore must take cover. He says we need to guard ourselves the same way Orion, the constellation, guards himself with a shield against the Taurids, because he confuses his computer software’s depiction of Orion with club and shield for an “official” image of Orion. The mythic figure is more frequently depicted as holding either a dead animal or a bow, and in either case wasn’t depicted that way at all in ancient Egypt, where he symbolized Osiris.
Harper then concludes that his revelation can help to save humanity if only we turn our attention to preparing for this event and recognizing the “electromagnetic/harmonic” nature of reality.