NavList:

Hello,

A theodolite can be oriented by observations of polaris in the northern hemisphere and these observations are covered in most surveying texts. However there is a simple method that works in either hemisphere. For due south you can first measure the altitude of a star as it passes through the crosshairs well to the east of south and note the direction from the theodolite. This direction is not yet an accurate direction, just a reference and will be adjusted later. Then measure the theodolite direction to the SAME star when it is west of south and it has the exact same elevation as when it was measured to the east. For this you can just leave the elevation as measured east of south clamped and adjust the theodolite direction only until the star goes through crosshairs again and note this direction. Direction one plus direction two divided by two is due south. So you can just set the theodolite to that calculated direction and it is in the meridian or pointed due south. This process takes a few hours but any star will work and you don't even need to know what star it is or it's declination or GHA just use the same star for both measurements. When using a star you don't even need to know anything about time or even have a watch. The sun or planets could be used but you would need to correct for changes in declination between the first and second sighting (that correction is covered in some surveying text books). 

That is my understanding of one method. Please let me know if this is wrong, confusing or there are better methods.

Thanks,

Doug