Apart from the fundamental function of providing astronomers with a reference frame to report their observations in, astrometry is also fundamental for fields like celestial mechanics, stellar dynamics and galactic astronomy.

Astrometric measurements are used by astrophysicists to constrain certain models in celestial mechanics.

These measured positions are then compared with those calculated by the laws of celestial mechanics: an assembly of calculated positions is often referred to as an ephemeris, in which distances are commonly calculated in astronomical units.

It was Pierre-Simon Laplace ( 1749 – 1827 ) who introduced a general version of the theorem and used it to approach problems in celestial mechanics, medical statistics, reliability, and jurisprudence.

Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed us to understand those laws.

The evidence was compiled by W de Sitter ( 1927 ) who wrote " If we accept this hypothesis, then the ' astronomical time ', given by the earth's rotation, and used in all practical astronomical computations, differs from the ' uniform ' or ' Newtonian ' time, which is defined as the independent variable of the equations of celestial mechanics ".

* central forces and celestial mechanics

* Sensors: camera with digital tape recorder ( about 20 pictures ), cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics

* Sensors: ultraviolet photometer, cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics

* Sensors: wide-and narrow-angle cameras with digital tape recorder, infrared spectrometer and radiometer, ultraviolet spectrometer, radio occultation and celestial mechanics.

* Sensors: wide-and narrow-angle cameras with digital tape recorder, infrared spectrometer and radiometer, ultraviolet spectrometer, radio occultation and celestial mechanics

* Sensors: twin narrow-angle cameras with digital tape recorder, ultraviolet spectrometer, infrared radiometer, solar plasma, charged particles, magnetic fields, radio occultation and celestial mechanics

In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers.

Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.

but fell out of favor compared to the parametric approach, which modeled phenomena as a physical system that was observed with error, such as in celestial mechanics.

His laws of motion were to be the solid foundation of mechanics ; his law of universal gravitation combined terrestrial and celestial mechanics into one great system that seemed to be able to describe the whole world in mathematical formulae.

In a more general usage in celestial mechanics, the expression ' tidal force ' can refer to a situation in which a body or material ( for example, tidal water, or the Moon ) is mainly under the gravitational influence of a second body ( for example, the Earth ), but is also perturbed by the gravitational effects of a third body ( for example, by the Moon in the case of tidal water, or by the Sun in the case of the Moon ).

An observation of a transit of Venus requires a huge range of auxiliary beliefs, such as those that describe the optics of telescopes, the mechanics of the telescope mount, and an understanding of celestial mechanics, all of which must be justified separately.

An observation of a transit of Venus is justified by its being coherent with our beliefs about optics, telescope mounts and celestial mechanics.

Calculations in celestial mechanics can also be carried out using the unit of solar mass rather than the standard SI unit kilogram.

The mathematical treatment of astronomy began with Newton's development of celestial mechanics and the laws of gravitation, although it was triggered by earlier work of astronomers such as Kepler.

Stieltjes originally wrote to Hermite concerning celestial mechanics, but the subject quickly turned to mathematics and he began to devote his spare time to mathematical research.

* In the technology and science of celestial navigation, lambda denotes the longitude as opposed to the Roman letter " L " which denotes the latitude.

Right ascension is the celestial equivalent of terrestrial longitude.

It begins when the Sun reaches the celestial longitude of 90 ° ( around June 21 ) and ends when the Sun reaches the longitude of 105 ° ( around July 7 ).

Xiàzhì more often refers in particular to the day when the Sun is exactly at the celestial longitude of 90 °.

It begins when the Sun reaches the celestial longitude of 270 ° ( around December 22 ) and ends when the Sun reaches the longitude of 285 ° ( around January 5 ).

Dōngzhì more often refers in particular to the day when the Sun is exactly at the celestial longitude of 270 °.

A sextant can also be used to measure the Lunar distance between the moon and another celestial object ( e. g., star, planet ) in order to determine Greenwich time which is important because it can then be used to determine the longitude.

Vega's proper motion is ( mas ) per year in right ascension — the celestial equivalent of longitude — and in declination, which is equivalent to a change in latitude.

In both astrology and historical astronomy, the zodiac ( Greek: ζῳδιακός, zōidiakos ) is a circle of twelve 30 ° divisions of celestial longitude that are centered upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year.

Essentially, the zodiac is a celestial coordinate system, or more specifically an ecliptic coordinate system, which takes the ecliptic as the origin of latitude, and the position of the sun at vernal equinox as the origin of longitude.

Babylonian astronomers at some stage during the early 1st millennium BC divided the ecliptic into twelve equal zones of celestial longitude to create the first known celestial coordinate system: a coordinate system that boasts some advantages over modern systems ( such as equatorial coordinate system ).

Similar to the terrestrial longitude and latitude, the equatorial system of right ascension and declination specifies positions relative to the celestial equator and celestial poles.

The ecliptic system of celestial longitude and celestial latitude specifies positions relative to the ecliptic.

Sidereal time, at any moment ( and at a given locality defined by its geographical longitude ), more precisely Local Apparent Sidereal Time ( LAST ), is defined as the hour angle of the vernal equinox at that locality: it has the same value as the right ascension of any celestial body that is crossing the local meridian at that same moment.

Objects are located in the night sky using right ascension and declination relative to the celestial equator ( analogous to longitude and latitude on Earth ), and when sidereal time is equal to an object's right ascension the object will be at its highest point in the sky, or culmination, at which time it is usually best placed for observation, as atmospheric extinction is minimised.

However, if two celestial bodies attain the same declination at the time of a conjunction in right ascension ( or the same ecliptical latitude at a conjunction in ecliptical longitude ), the one that is closer to the Earth will pass in front of the other.

On the celestial sphere, positions are located by latitude and longitude.

The coordinate α corresponds to longitude measured from the vernal equinox V, the point on the sky where the Sun crosses the celestial equator on near March 21.

The latitude and longitude of that point is known as the celestial body ’ s geographic position ( GP ), the location of which can be determined from tables in the Nautical or Air Almanac for that year.