Convert Sidereal Years to Anomalistic Months
Convert Sidereal Years (a_sid) to Anomalistic Months (anom.mo) instantly and accurately.
Conversion Formula
anom.mo = a_sid × 13.25575446
About Sidereal Years
The sidereal year = Earth's orbital period relative to the stars = 365.25636 days = 31,558,149.8 s - about 20 min 24 s longer than the tropical year. The gap arises from precession of the equinoxes (~50 arcsec/year westward drift), which causes the tropical year to end slightly before the sidereal orbit completes. JPL DE440 ephemerides and J2000.0 epoch are anchored to the sidereal frame. 1 a_sid = 365.25636 d.
About Anomalistic Months
The anomalistic month = interval between successive Moon perigees = 27.5546 days = 2,380,713.2 s. Slightly longer than the sidereal month because the Moon's perigee precesses, completing one revolution in ~8.85 years. Governs 'supermoons': a full moon at perigee appears ~14% wider and 30% brighter. Tidal forces at perigee are ~30% stronger than at apogee. 1 anom.mo = 27.5546 d.
Quick Reference Table
| Sidereal Years (a_sid) | Anomalistic Months (anom.mo) |
|---|---|
| 1 a_sid | 13.2558 anom.mo |
| 2 a_sid | 26.5115 anom.mo |
| 5 a_sid | 66.2788 anom.mo |
| 10 a_sid | 132.558 anom.mo |
| 25 a_sid | 331.394 anom.mo |
| 50 a_sid | 662.788 anom.mo |
| 100 a_sid | 1325.58 anom.mo |