Sidereal Day to Hours
Convert astronomical sidereal days—measured relative to distant stars—into familiar Earth hours for mission planning or stargazing.
Values are based on the mean sidereal day. Consult official ephemerides for mission-critical timing.
Examples
- 1 sidereal day ⇒ 23.9345 hours
- 2.5 sidereal days ⇒ 59.8362 hours
- 0.1 sidereal day ⇒ 2.3934 hours
FAQ
Why is a sidereal day shorter than 24 hours?
Because Earth rotates once relative to distant stars in about 23.9345 hours, while a solar day includes the extra rotation needed to face the Sun again.
Where is sidereal time used?
Astronomers rely on sidereal time to point telescopes accurately, and satellite operators use it to synchronize observations with Earth's rotation.
How precise is this conversion factor?
The constant 23.9344696 hours reflects the mean sidereal day. Variations of milliseconds occur due to tidal forces and leap seconds.
Additional Information
- Sidereal time tracks Earth's rotation relative to distant celestial objects, which is useful for telescope alignment.
- A solar day is longer because Earth orbits the Sun; it must rotate slightly more than 360° for the Sun to reach the same position in the sky.
- For high-precision work, use more decimal places or updated astronomical constants published by the International Earth Rotation Service.