In my article (this Journal, 1, 290, 1948) on The Provision for Astronomical Navigation at Sea I called attention (p. 302) to the possible advantages of dividing the standard PZS triangle of astronomical navigation into two right-angled (or quadrantal) triangles by a perpendicular (or quadrantal arc) from the pole P to ZS, or ZS produced. In particular I wrote ‘the method is one which might be further explored,…’; it is only recently that I have had occasion to do so. As far as I have been able to discover from the material available to me (including, by courtesy of Captain Charles H. Cotter, a copy of the typescript of his A History of Nautical Astronomical Tables), the only published method or tables using this principle is ‘Tables for the Abbreviated Computation of Zenith Distance and Azimuth of Celestial Bodies’, by Frane Flego (Split, 1957). Unfortunately, as pointed out by W. A. Scott and myself in a review article (this Journal, 11, 207, 1958), Captain Flego failed to overcome some of the technical difficulties of the method.