Moon

In the case of the moon, Moshier's ephemeris uses a modified version of the lunar theory of Chapront-Touze and Chapront which is within 0.5" in longitude, 0.33" in latitude, and 0.36 kilometers in distance of DE404 from -1369 to +3000. Compared with DE406 (HORIZONS) there are differences shown in the graphs for geocentric longitude, latitude, and distance in which the units are seconds for longitude and latitude and kilometers for distance. The differences for longitude have their minimum of less than 2" in the twentieth century and rise to +5" approaching +3000 and to +190" approaching -2999. Since uncertainties in delta T at early periods are in hours, while a difference of 190" = 3' 10" in longitude corresponds to about 6 minutes in time, these are still very small differences. And of course there are no observational criteria for selecting between the lunar theories in Moshier's ephemeris and DE406. We have nevertheless supplied a correction for the differences in longitude using a fourth-order polynomial with results shown in the graph 'Moon: geocentric longitude (corrected)'. This correction is optional and is selected by checking the box moon under apply correction in the More settings dialog . Latitude and distance cannot be corrected in this way, so have the differences shown in the graphs. The range of differences in uncorrected and corrected longitude and uncorrected latitude in seconds and distance in kilometers for selected periods computed by the ephemeris is as follows: