Convert Sidereal Days to Draconic Months

Convert Sidereal Days (sid.d) to Draconic Months (drac.mo) instantly and accurately.

Conversion Formula

drac.mo = sid.d × 0.03664785769

About Sidereal Days

A sidereal day = Earth's rotation period relative to the stars = 23 h 56 min 4.0905 s = 86,164.0905 s - ~3 min 56 s shorter than the 24 h solar day because Earth advances ~1° in its orbit each day. Equatorial telescope mounts rotate at one turn per sidereal day to track stars. VLBI, GPS orbit determination, and polar-motion monitoring use sidereal rotation as their reference. 1 sid. day = 86,164.0905 s.

About Draconic Months

The draconic (nodical) month = 27.2122 days = 2,351,135.8 s - the interval between successive Moon passages through the same orbital node. Named from the Latin 'draco' (dragon): eclipses only occur near the nodes, where the Moon can align with the Sun or Earth's shadow. The Saros cycle (18 yr 11 d) equals ~242 draconic months, enabling eclipse sequence forecasting. 1 drac.mo = 27.2122 d.

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