Dirty Skies

I determined today from looking at nautical charts for the Tampa Bay area that magnetic north is actually 4°15′ W (west) of true north in my area. I would have to take this into account when polar aligning the scope with a compass. Polaris is usually very low on the horizon at this latitude and lost in skyglow.

I thought this was interesting. I mean I knew magnetic north and true north weren’t the same but it didn’t occur to me that depending on where you were on the surface of the Earth there could be further deviation from variations in the planets mass distribution, crust thickness and field line orientation.