Celandra has two moons, which for the moment I'll call Maxiluna and Miniluna. Maxiluna is larger and closer with an orbital period of 28 days, while Miniluna is much smaller and farther out, with an eccentric orbit having a period of 236 days. Interestingly, 28/236 = 7/59. This means that Maxiluna completes 59 orbits in the same time that Miniluna completes 7 orbits. Assuming that at time t=0 days that both moons (Mx, Mn) are at new moon phase, beginning their cycles (Mx=0, Mn=0), we can create this table: ------------------------------------- | t | Mx | Mn | Phase | ------------------------------------- | 0 | 0 | 0 | New | | 413 | 1.75 | 14.75 | 3rd Quarter | | 826 | 3.5 | 29.5 | Full | | 1239 | 5.25 | 44.25 | 1st Quarter | | 1652 | 7 | 59 | New | ------------------------------------- The two moons will be in exactly the same phase every 413 days after t=0 (every 1 year, 1 month, 18 days). They will complete a great cycle (7 orbits to 59 orbits) every 1,652 days (4 years, 6 months, 11 days). To put it another way, for any given combination of Maxiluna and Miniluna's phases, the combination will repeat exactly every 1,652 days. Andrew ---------------------------------------------------------------- To unsubscribe, send mail to celandra-off@phoenyx.net.
