Buffalohenge

The streets. Every named road inside the Buffalo city line comes from OpenStreetMap. A street is not the unit of measurement here, because a henge needs an unbroken sightline and most of Buffalo's long streets bend somewhere. The unit is a straight run: the longest stretch of a street that never wanders more than 10 metres off its own chord. Runs shorter than 500 metres are dropped, because at that length you are looking at a block, not a vista. Clinton Street produces three separate runs on three different bearings, and each gets its own dates.

The sun. Position comes from the NOAA solar equations, with the standard atmospheric refraction correction applied. The moment quoted is the one Neil deGrasse Tyson uses for Manhattanhenge: the centre of the sun sitting on the horizon, half above and half below. That lands a few minutes before the sunset time your weather app shows, which waits for the last sliver of the upper edge to disappear.

How close counts. The sun is about half a degree wide. An alignment is called dead centre when the street's axis passes within a quarter of a degree of the sun's centre, which is to say the line of the road still lands on the visible disk. Buffalo's grid is fine enough that most streets have a neighbour within that tolerance, so a good evening usually lights up a dozen roads at once.

What this does not know. It assumes a flat, open horizon, which is generous. A real sightline can be closed off by a building at the far end, a rise, a stand of trees, or the elevated lanes of the 190. The date and the minute are exact; whether you can actually see it from where you are standing is a question for your own two feet. Buffalo does at least have the flattest possible excuse: for the streets aiming west-southwest, the horizon is Lake Erie.