Resources like this (and as others have mentioned, Dark Site Finder) are very useful for astrophotography, especially for a hobbyist like myself. Many don't realize how relatively close they live to areas with great nighttime viewing conditions. For example, upstate New York has some great viewing locations, so even if you live in NYC it's an easy weekend trip. Here's a shot I took of the Milky Way taken from such a…
Especially essential is planning for dark skies in the direction of whatever it is you are trying to shoot, which is in some cases arguably slightly more important than the dark sky level of where you are standing. If a galaxy rises over a city, it's going to be hard to image even if you're far from the city.
One of the tools I use the most is an app called "PlanIt Pro", which gives you pretty much all the info you need, including being able to show where in the sky various astronomical objects are, their magnitude, a VR simulation of them with the 3D topo map, and lots of other things. It also has a light pollution map built-in, and can show you the position of the Milky Way. I plan many of my shots with it. There's a free version and I can't remember which features are omitted from that but it's been worth every penny for me.