Plane of reference

reference planeplaneplanes
In celestial mechanics, the plane of reference (or reference plane) is the plane used to define orbital elements (positions).wikipedia
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Orbital inclination

inclinationinclinedtilted
The two main orbital elements that are measured with respect to the plane of reference are the inclination and the longitude of the ascending node.
It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object.

Longitude of the ascending node

right ascension of the ascending nodelongitude of ascending nodenode
The two main orbital elements that are measured with respect to the plane of reference are the inclination and the longitude of the ascending node.

Ecliptic

ecliptical orbitsecliptic planeplane of the ecliptic
This plane of reference is coplanar with Earth's orbit around the Sun (and hence the Sun's apparent path around Earth).

Celestial equator

equatorialequatorial planeequatorial sky
This plane of reference bases the equatorial coordinate system.

Fundamental plane (spherical coordinates)

fundamental planefundamental planes
The fundamental plane in a spherical coordinate system is a plane of reference that divides the sphere into two hemispheres.

Celestial sphere

celestialcelestial hemispherehemisphere
Certain reference lines and planes on Earth, when projected onto the celestial sphere, form the bases of the reference systems.

Celestial mechanics

celestialcelestial dynamicscelestial mechanician
In celestial mechanics, the plane of reference (or reference plane) is the plane used to define orbital elements (positions).

Orbital elements

orbital parametersorbital elementKeplerian elements
In celestial mechanics, the plane of reference (or reference plane) is the plane used to define orbital elements (positions).

Longitude

WestlongitudinalE
On the plane of reference, a zero-point must be defined from which the angles of longitude are measured.

Hour circle

This is usually defined as the point on the celestial sphere where the plane crosses the prime hour circle (the hour circle occupied by the First Point of Aries), also known as the equinox.

First Point of Aries

sun passes into the constellation Aries
This is usually defined as the point on the celestial sphere where the plane crosses the prime hour circle (the hour circle occupied by the First Point of Aries), also known as the equinox.

Equinox

autumnal equinoxautumn equinoxequinoxes
This is usually defined as the point on the celestial sphere where the plane crosses the prime hour circle (the hour circle occupied by the First Point of Aries), also known as the equinox.

Invariable plane

common orbital alignmentinvariable plane of the Solar System“invariable” axis

Solar System

outer Solar Systeminner Solar Systemouter planets

Semi-major and semi-minor axes

semi-major axissemimajor axissemi-major axes

Lunar precession

precess18.6 and 8.85 yearslunar apsidal precession
Lunar precession is the change in orientation of the lunar rotational axis with respect to a reference plane, following the normal rules of precession followed by spinning objects.

Azimuth

azimuthalazimuthal angleazimuth angle
The vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane; the angle between the projected vector and a reference vector on the reference plane is called the azimuth.

Orbital node

Nodeascending nodenodes
An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined.

Normalhöhennull

NHNsea level (NHN)sea level
In geographical terms, NHN is the reference plane for the normal height of a topographical eminence height above mean sea level used in the 1992 German Mean Height Reference System (Deutsches Haupthöhennetz).

Epoch (astronomy)

J2000J2000.0epoch
These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit.

Non-inclined orbit

equatorial orbitequatorialEcliptic orbit
A non-inclined orbit is an orbit coplanar with a plane of reference.

Orbital plane (astronomy)

orbital planeorbital planesplane of its orbit
The orbital plane is defined in relation to a reference plane by two parameters: inclination (i) and longitude of the ascending node .

Bow and warp of semiconductor wafers and substrates

Bow is the deviation of the center point of the median surface of a free, un-clamped wafer from the reference plane, where the reference plane is defined by.