It is probable that the astronomers who erected these standing stones were from the same community as the builders of Newgrange. Baltray may have taught the Neolithic builders an important lesson. Here, at the Boyne estuary, looking out at the sunrise on the shortest day, we have often seen that, even on a clear morning, there is regularly a thin strip of clouds which hugs the horizon along the sea. This obscures the cloud for the first seven or eight minutes, so the critical moment where the sun creeps up out of the sea is missed. At Newgrange, the monument is positioned so that it's alignment towards the sun collects sunlight about 15 minutes or so later than the moment of sunrise at Baltray. In effect, the hill called Red Mountain across the valley from Newgrange provides a false horizon, and allows the sun that critical time to clear the horizon-hugging cloud which no doubt would obscure the sunrise if that false horizon was not in place.

Nevertheless, a competent astronomy requires the moon and stars for accurate time-keeping, so it is unlikely the stone builders used sun alone to regulate the year. Plenty of evidence of this is outlined in Island of the Setting Sun - In Search of Ireland's Ancient Astronomers.

Dowth's chamber aperture allows for a much wider range of sun events than the narrow and lengthy Newgrange chamber. The afternoon sunlight comes into Dowth South from October until February, Anne-Marie Moroney has found.

In Island of the Setting Sun, Anthony Murphy and Richard Moore propose that Dowth was a lunar structure as much as it was solar. The chambers of Dowth allow moonlight in on critical dates during the moon swing cycle, at the time of Major Standstill and Minor Standstill, terms coined by the late Alexander Thom. Basically, these are the lunistices, where the moon appears to reach its extremes during its 18.6-year cycle.