The equatorial plane, an astronomical term, refers to the plane where the earth's equator lies.Satellite orbitThe plane is called the orbital plane, which always passes through the center of the earth.The angle between the orbital plane and the equatorial plane of the earth is called the orbital inclination.
The plane where the earth's equator lies is called the equatorial plane, that is, the plane passing through the earth's center and perpendicular to the earth's axis.The equatorial plane in a narrow sense refers to the plane between the equator and the center of the earth.The equatorial plane of the earth expands infinitely and intersects with the celestial sphere, which is called the celestial equator.[1]
The plane between the celestial equator and the geocenter is the generalized celestial equator plane.The plane where the satellite orbits is calledTrack plane, the track plane always passes throughearthCenter of.The angle between the orbital plane and the equatorial plane of the earth is calledRail inclination。
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astronomerTherefore, take the ground observation point as the center, and take the infinite length as theradius, onuniverseSpace makes an imaginary sphere, called the "celestial sphere".The equatorial surface of the earth expands infinitely, and the great circle intersecting the celestial sphere is the celestial equator.The celestial equatorial plane andEclipticThe planes do not coincide, and there is an angle of 23 ° 26 'between them, commonly known as“Yellow declination angle”。In addition, the celestial equator and the ecliptic have two intersections, namely, the equinox andAutumnal equinox。The intersection of the sun along the ecliptic from the southern hemisphere to the northern hemisphere is called the vernal equinox, and the intersection of the sun from the northern hemisphere to the southern hemisphere is called the autumnal equinox.
The sun passes the vernal equinox on or about March 21 every year. On this day, the sun shines directly on the earth's equator. The days and nights around the world are almost the same length, which is customarily called the equinox.Astronomically, this day is the beginning of spring in the Northern Hemisphere.
The intersection line between the plane where the Earth's equator lies and the celestial sphere is a big circle, which is called the "celestial equator", and it is the projection of the equator on the celestial sphere.
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Plan of celestial equator
The celestial sphere is an imaginary sphere. It is inconvenient to draw three-dimensional figures when drawing.In order to facilitate the drawing and make the points and lines related to the celestial sphere clear at a glance, the celestial sphere figure must be drawn as a plan.The celestial axis is infinitely lengthened, and related points and lines on the celestial sphere are projected one by one from a point in the extreme distance on the celestial equatorial plane. This figure is called the celestial equatorial plane map.
Polar equatorial plane
The spherical projection of the plane on the crystal is all circular, and the polar equatorial plane projection still takes the S pole as the viewpoint. Connect the circular track on the spherical surface with the S pole, and the intersection line of the line and the projection plane is the polar equatorial plane projection of the plane.The spherical projection of the plane passing through the projection center is a large circle concentric with the projection sphere in the same diameter. There are three cases of polar equatorial plane projection:[2]
1. The projection of the polar equatorial plane of the horizontal great circle is the base circle;
2. The projection of the polar equatorial plane of the vertical large circle is the diameter of the base circle;
3. The polar equatorial plane of the inclined large circle is projected as a large arc with the diameter of the base circle as the chord.
