By looking at the diagram furnished you when we were talking of sidereal time, all this becomes perfectly clear.
This is sidereal time which agrees with mean time on March 22d, and gains on the latter at the rate of two hours a month.
The sidereal time at any moment is the right ascension of the hour circle which at that moment coincides with the meridian.
When the hour circle passing through Sirius coincides with the meridian, the sidereal time is 6h.
He assigns the Parthenon to a hill of ages, and the temples of Upper Egypt to sidereal time.
Having set the clock approximately to sidereal time, observe one or two more stars in the same way as above.
sidereal time was determined by observing transits of stars over a meridian line actually laid out upon the ground, etc.
If the clock gains or loses with respect to sidereal time, take this into account in the value of U.
After understanding its construction, extract the sidereal time at Noon for the day of your birth and refer to the next chapter.
One can not tell off-hand whether 10 hours, sidereal time, falls in the day or in the night.
|sidereal time |
Time based on the rotation of the Earth with respect to the background of fixed stars. Astronomers generally use sidereal time rather than solar time because it is better suited to observations beyond the solar system. ◇ A sidereal day is the time required for one complete rotation of the Earth on its axis with respect to a fixed star. It is an unvarying unit equal to 23 hours, 56 minutes, 4.09 seconds of solar time. ◇ A sidereal month is the average period of revolution of the Moon around the Earth with respect to a fixed star, equal to 27 days, 7 hours, 43 minutes of solar time. ◇ A sidereal year is the time required for one complete revolution of the Earth around the Sun with respect to a fixed star, equal to 365 days, 6 hours, 9 minutes, 9.54 seconds of solar time. Compare solar time.