Posted by Norman Lavender at 07:12 on 2011 Mar 13
Thank you Callum and Andrea.Having re-read the statement in the book it does follow on from a description of the alt-azimuth mount and describes the equatorial mount as an alt-azimuth tipped over. From that point of view it would appear it is indeed talking about measurement from the zenith.However for a novice this is a bit confusing as in most descriptions of polar alignment (i.e. in Norton’s Star Atlas") explicitly refers to the angle relative to the horizontal.