does anyone know what digital compass would be suitable to setup a Pier so its pointed at the south pole? I need to it be accurate because i want to do imaging with a C14.
Any of them should be alright. But you also have to remember in setting up your pier that you align it with true south, not magnetic south. Do you know your magnetic declination for your observing site??
A much more accurate method to find true South is to use the solar transit method. Use your favorite planetarium program to determine when the Sun transits the meridian on the current date. Use a ladder and some string to suspend a plumb bob over your pier location. At the exact minute the Sun transits the meridian, draw a line along the shadow of the string. The line will be exactly North-South within a fraction of a degree. This is far more accurate than any compass, analog or digital. Nor is it affected by nearby ferrous metals such as rebar, etc.
