Not every claimed astronomical alignment in prehistoric monuments holds up, and saying so honestly is part of what makes the real cases credible. Alexander Thom's mid-twentieth-century surveys of British and Irish megalithic sites proposed an extraordinarily precise prehistoric observatory tradition, including claimed sightlines accurate to a fraction of a degree across dozens of sites, implying a sophisticated shared astronomical science across Neolithic Britain.
Clive Ruggles's later, more rigorous statistical re-survey found that most of Thom's claimed precise alignments do not survive careful testing once the sheer number of stones and possible sightlines at a large site is accounted for; with enough stones in a ring, some alignment to some solar or lunar event is close to guaranteed by chance alone; and Ruggles showed that the genuinely secure cases are fewer, cruder in precision, and more plausibly seasonal or ceremonial markers than a working scientific instrument.
What remains after that correction is still real and still remarkable. Stonehenge's main axis is reliably aligned to the midsummer sunrise and midwinter sunset, a deliberate choice repeated at other major sites. Newgrange's passage is built so that only at the winter solstice does the rising sun's light travel down its full length to illuminate the inner chamber, a feat of construction planning that could not be accidental. The honest picture is narrower than Thom's but no less genuine: real solstice-watching, real monumental planning, and real astral religious meaning, without needing to claim more precision than the stones themselves can support.