Comparison of the Moon at Perigee and Apogee           This is comparison of the Moon at perigee and apogee. Because the lunar orbit has an eccentricity of 0.5490049 Cox-305, its distance varies by about 11 % from perigee to apogee. This means that the Moon's angular diameter decreases from perigee to apogee by about 11 %. The perigee-apogee comparison figure illustrates this point. The difference is rather striking, but it isn't noticed because humans have difficulty telling sizes without a standard of comparison and, of course, we never see perigee and apogee Moons together.

          The one time we can notice the variation in lunar angular diameter is during TOTAL/ANNULAR SOLAR ECLIPSES: the Moon's angular size must be smaller during an annular eclipse than during a total eclipse. During total/annular solar eclipses, the Sun provides a standard of comparison.

          There are some further complications to the changing angular diameter of the Moon that are well discussed in at the image credit site.

Credit: John Walker's Inconstant Moon page. John Walker has declared this page and its images public domain.