The native is the topic of the occurrence being mapped at a specific moment and position, and is regarded to be at the centre of the zodiacal sphere.
The celestial sphere is an imagined orb onto which the planets, zodiac and constellations are projected. The plane of the skyline is centred on the native, and is lateral to the world at that position. In a circle whose radius is substantially large, this plane may be treated as an almost equivalent to the corresponding plane with its midpoint at the Earth's core. This largely makes simple the geometry of the horoscope, but does not consider that the native is in movement. Some writers on horoscope have thus taken into account the influences of parallax, but majority would concur that they are comperatively minor.