Sidereal Time

Sidereal time, or “star time,” is based on Earth’s rotation relative to the stars, rather than to the Sun. The sidereal day is almost 4 minutes shorter than our 24-hour day. 

When navigating by the stars, an observer will see the same constellation at the same place in the sky about four minutes earlier than the night before.

Caption:
Sidereal time, or “star time,” is based on Earth’s rotation relative to the stars, rather than to the Sun.
Type: Illustration
Image Date: 2012
Credit: National Air and Space Museum, Smithsonian Institution
Origin: National Air and Space Museum, Smithsonian Institution
Creator: Bruce Morser
Navigation Methods
 
Sidereal time, or “star time,” is based on Earth’s rotation relative to the stars, rather than to the Sun.