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Published online by Cambridge University Press: 18 January 2010
Over thirty-seven years have passed since the writer published his ‘Wrinkles in Plane Chart Methods’, explaining the value and use of his then new ‘Protractor Diagram’ and ‘Graduated Triangle’ for plotting lines of position on squared paper. A figure showed the simplicity of the solution, overcoming the difficulty of the use of different units for the differences of latitude and longitude.
It is now proposed to present a further ‘wrinkle’ to facilitate the use in navigation of six prominent equatorial stars, particularly Mintaka (δ Orionis) which is only 2o′ south of the equator, and practically a fixed star since its annual (precessional) variation in declination is only 2″·67. It is one of the three stars of Orion's belt and its magnitude is 2·5, slightly fainter than Polaris.