Hansen's Improved Ex-Meridian Tables By C.H. Cotter
Latitude by ex-Meridian altitudes is as necessary as observations for longitude, but as the sights should be frequent to ensure accuracy, the ordinary methods are tedious.
The general principle upon which the tables are calculated is that the corrections in each following table is slightly less than in the previous, the difference between any two consecutive tables is only 1' in an hour angle of 15' (where the tables extend to that angle).
The introduction of Local Hour Angle in are, instead of in Time, has made necessary a revision in the layout of these tables. In all cases the tables are entered with the L.N.A. of the heavenly body observed. It is confidently expected that the necessary innovation will commend itself to navigators.
An observation may be taken out by sight without any interpolation whatsoever. They are calculated from Latitude 60' N. to 60' S., and declination up to 23'., and are equally applicable for Moon, Stars or Planets, when their declinations do not exceed 23' N. or S. Masters, Trimmers, Stevedores, etc, will find the tables of great value.