That's the observer's 'zenith'. Since it's referenced to the
"observer's head", each observer has a different zenith.
Usually, it is Polaris, the North Star. So technically, it's not "imaginary".
That is called the "zenith". And the opposite point, underneath your feet, is called the "nadir".
zenith
The north celestial pole.
the "zenith"
North Celestial Pole
The zenith.
zenith
zenith
The zenith.
The microscope has two systems of lenses: the ocular lens into which the observer looks; and objective lenses placed directly above the object being observed.
yes
yes
This is known as the epicentre.
The zenith.
Zenith
The celestial equator is an imaginary circle created by extending Earth's equator into space. Zenith is an imaginary point in the sky directly above and observer on earth.
That's called the observer's "zenith".
The epicenter is the point on the earth's surface directly above the earthquake's origin.
The microscope has two systems of lenses: the ocular lens into which the observer looks; and objective lenses placed directly above the object being observed.
The hypocentre is the point inside the Earth where an earthquake starts. The point on the Earth's surface directly above this is the epicentre.
The point just overhead is called the zenith. The objects visible at that point depend on the date, the time of day or night, and the observer's location.
The zenith is the direction directly above the observer. The astronomical horizon is the plane that is perpendicular to that direction, i.e. horizontal. The "true horizon", however, is the cone from the observer to the point on the earth, below which you can not "see over", so it is a small amount lower in angle. In practice, the two horizons can be considered to be the same, because the height of the observer is often small in comparision to the diameter of the earth, unless the observer is standing on a tall point, such as a mountain.
The point on the Earth's surface directly above an earthquakes focus or hypocentre is the epicentre.
mantle
Almost directly above the North Pole.