Inspired by some recent threads concerning finding "true" north, I did some reading at the beach last week. I wondered if there are pairs of NGS marks suitable for practicing sun shots and Polaris shots. It turns out that there are many pairs of marks nearby that are within a fraction of a second of forming due North-South geodetic lines. Problem is, they're too far apart, separated by trees, on bridges, on railroad rights-of-way, or otherwise problematic.
But down in Whiteville, NC, there's an airport that has a CBL. Now the CBL does not run north-south, but its zero point is about 280, + or -, feet from a secondary airport control monument and the pair is within about 0.2 second from being on a north-south line.
Here's a Google Earth picture:
Maybe a good place to see how good your sun and Polaris shots are? Or maybe there's a useful pair near you.