computation of observer position in astro-navigation

 Nautical ephemeris are included until 2030 with no relevant error for
 all navigational bodies, 56 stars, Sun, Moon and 4 major planets.
 The local meridan time can be computed directly from time UT: sextant
 altitude correction is computed automatically after inserting the
 value of height of eye with the correction tables of the Admiralty
 Nautical Almanac.
 .
 A plotting sheet reports the calculated position and bodies' position
 lines. An info window indicates the body's most important celestial
 parameters.