Get out your phones and head down to street level, because this year’s final Manhattanhenge — the coincidental phenomenon where the sun aligns perfectly with Manhattan’s rectangular street grid — is taking place this weekend, Sat. July 11 through Sun. July 12. And while the point of the naturally occuring event is that you don’t have to work very hard to find the best viewing locations, not all east-west blocks are created equal. Some clouds may interrupt tonight’s show, according to Accuweather, but there’s no rain in the forecast around sunset (8:28pm) on either day. Here’s everything you know are a few tips on the best viewing locations and happenings around town this weekend. First up, on Saturday, American Museum of Natural History is hosting a free block party from 3-10 p.m. on W. 79