NavList:

While this puzzle was proceeding, I couldn’t help feeling rather smug, because in an aircraft with a calibrated periscopic sextant mount you can take heading check at any time.  In fact, we got one for free every time we took a shot.  The poor old pilots must have been suffering from information overload.  “, and our heading is …….”. 

Then, I began to wonder why 250 years ago some enterprising mariner didn’t make a cage to get an exact bearing of the Sun so that they could do the same.  It was at that stage that I realised that amplitude bearing is a bit of a ‘free-bee’ falling into the latitude from the Sun at noon, or from Polaris category.  What is the one important piece of navigation information you don’t need to complete amplitude by the Sun at sunrise/set calculations?  DaveP