Northern Celestial Hemisphere
The Northern Celestial Hemisphere or the Northern Sky, is part of a rotating astronomical region in the sky. It is the northern hemisphere of the celestial sphere.
Astronomy
In the context of astronomical discussions or writing about celestial mapping, it may also simply then be referred to as the Northern Hemisphere.
For the purpose of celestial mapping, the sky is considered by astronomers as the inside of a sphere divided in two halves by the celestial equator. The Northern Sky or Northern Hemisphere is therefore that half of the celestial sphere that is north of the celestial equator. Even if this one is the ideal projection of the terrestrial equatorial onto the imaginary celestial sphere, the Northern and Southern celestial hemispheres must not be confused with descriptions of the terrestrial hemispheres of the Earth itself.
Visibility from the Southern terrestrial hemisphere
Due to the angled rotation of the Earth relative to the ecliptic, parts of the Northern Sky are visible from the Southern terrestrial hemisphere at certain times of the year.