Convert Day (Sidereal) (d (sidereal)) to Hour (Sidereal) (h (sidereal)) instantly.
About these units
Day (Sidereal) (d (sidereal))
A sidereal day is the time Earth takes to rotate exactly 360 degrees relative to the distant stars—about 23 hours, 56 minutes, 4 seconds. In contrast, the solar day is slightly longer because Earth advances in its orbit each day and must rotate extra degrees for the Sun to appear in the same position in the sky. Sidereal days are fundamental to astronomy: telescopes use sidereal time to track stars, which appear in the same position in the sky at the same sidereal moment each night. This unit anchors astronomical observation to the cosmos rather than to the Sun.
Hour (Sidereal) (h (sidereal))
A sidereal hour is 1/24 of a sidereal day, approximately 59 minutes and 50.17 seconds of solar time. Astronomers use sidereal hours to measure right ascension and to coordinate telescope pointing systems. Because stars return to the same apparent position after exactly one sidereal day, sidereal hours offer a stable celestial reference frame. While not used in daily life, sidereal hours are indispensable for precision observation of the universe.