So today, we have a “supermoon”, which is a situation where the Moon appears largest from Earth, the vernal equinox, and a solar eclipse across large parts of Europe.
What would the ancients, especially the ones with the sophisticated astronomical observations, have made of this?
The druids aren’t prehistoric (or a people: they’re an occupation or at most a class within a group of related historical peoples), but we don’t have any idea what they would have made of the various moons. There simply isn’t much data from which to extrapolate. That doesn’t stop people from trying, of course.
We don’t even know that the ancient Celts celebrated the equinox and solstice, though popular culture now takes it as read that they did. And they could have—they certainly knew when they occurred—it’s just that evidence is scarce.
They probably wouldn’t have had a specific name for it, but they probably would see it and say "Oh yeah, that thing, when the moon does this-that-or the-other, we called it “whatever”
The moon isn’t really all that unpredictable so I assume whatever happens to us happened a lot to them as well
The ones in Southern Sweden would have decreed that “rain still sucks”.
Except if they were like my coworker Ulf, who claims that “I am mighty! Viking! and you are all weenies.”
IOW, the cloud cover made any fancy phenomenons invisible.
I haven’t heard of anyone prior to 1979 saying anything about the “supermoon”. (Technically it will be a micromoon when it’s a full moon, as a supermoon is a full moon that happens when the moon is near perigee) They might have noticed annular solar eclipses, which happen when the moon is near apogee, but I haven’t heard of anyone having myths specifically about annular eclipses (as opposed to about solar eclipses in general). A supermoon is not that much bigger than an average full moon, so it’s not that surprising that ancient peoples didn’t find them noteworthy.
A solar eclipse when the moon is near perigee is not that noticeably different from one where the moon is a little further away. A solar eclipse that happens when the moon is near apogee is notable for being an annular eclipse instead of a total eclipse.
Of course, a lot of the ancient peoples who saw solar eclipses would have seen partial eclipses. The difference between a partial eclipse that is total somewhere else and one that is annular somewhere else is not particularly notable.
I’m not sure if any ancient peoples thought that a solar or lunar eclipse occurring on the vernal equinox was more noteworthy than any other eclipse.