FS2004 Simulated Aircraft Bubble Sextant. As travel by air developed and matured, navigation over long distances also developed and improved. In the early days, however, air navigation essentially used ship navigation techniques adapted for aircraft. Without "landmarks", the navigators used ded reckoning (DR) and the stars. Celestial or astronomical navigation provides a means of obtaining lines of position (LOPs) from the stars. Crossing LOPs will fix a position. It requires a chart, and a planned course on that chart, with waypoints specified by latitude and longitude, an assumed time of arrival at each waypoint, and stars (including the sun, moon, or planets) in view. In the 1940s, extensive tables of star positions were made available to air navigators to be used with sextants to obtain these LOPs. In the tables, all times involved are GMT. This data is available from the Internet in "ready to use" form. This gauge simulates the sextant, and the process by which one obtains a LOP, or crossing LOPs to obtain a position, or fix. Can be used with any FS2004 aircraft. Includes comprehensive browser-based manual and references. By Dave Bitzer and Mark Beaumont.