A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2015 Oct 27, 01:53 -0700
Steven Wepster has published some precomputed lunar distance tables here. Andres Ruiz González has also produced an excellent app for android phones (available here) which gives hourly distances for any of a number of selected bodies. And yes, the angular size of the moon is very important when doing lunars. The semi-diameter can be found in the Nautical Almanac or determined with the equation: SD= 0.2724 · HP. (HP [Horizontal Parallax] can, in turn, be found in the N.A., or calculated by the equation: sin(HP)= radius of the Earth/distance to the moon.) Calculating the SD is preferred since the N.A. only gives SD for each day, whereas HP is given for each hour. In addition to the SD, one must take into account the 'augmentation' of the moon's apparent size. This is due to the moon being slightly closer to the observer as it increases in altitude and can be calculated using the formula: 0.3 · sin(Height of the moon). The SD of the sun changes very slowly, so the figure given for each three day period in the N.A. should suffice. Stars, of course, have no apparent diameter. But I believe there are some cases in which, when using a planet (such as Jupiter), you'll want to try and "split" the planet with the limb of the moon.