Top comment is basically saying, "your joke is lame, and this devalues the significance of Stonehenge." Some of the "wider audience", who may or may not be familiar with Stonehenge's properties, may in fact conclude, "so Stonehenge is basically BS like this?"
It's a bit of an over-wrought setup for what is basically a tip on when to get the sun just right for a nice photo in Manhattan. Still appreciate the tip, though. The setup is no doubt amusing to some and not others. I feel like for this kind of thing, both camps' opinions are perfectly valid, since it's a matter of personal preference. And that the "negative" opinion was expressed in a HN thread is... not surprising in the least.