Astronomical in the context of Comet

A laser guide star is an artificial star image created for use in astronomical adaptive optics systems, which are employed in large telescopes in order to correct atmospheric distortion of light (called astronomical seeing). Adaptive optics (AO) systems require a wavefront reference source of light called a guide star. Natural stars can serve as point sources for this purpose, but sufficiently bright stars are not available in all parts of the sky, which greatly limits the usefulness of natural guide star adaptive optics. Instead, one can create an artificial guide star by shining a laser into the atmosphere. Light from the beam is reflected by components in the upper atmosphere back into the telescope. This star can be positioned anywhere the telescope desires to point, opening up much greater amounts of the sky to adaptive optics.

Because the laser beam is deflected by astronomical seeing on the way up, the returning laser light does not move around in the sky as astronomical sources do. In order to keep astronomical images steady, a natural star nearby in the sky must be monitored in order that the motion of the laser guide star can be subtracted using a tip-tilt mirror. However, this star can be much fainter than is required for natural guide star adaptive optics because it is used to measure only tip and tilt, and all higher-order distortions are measured with the laser guide star. This means that many more stars are suitable, and a correspondingly larger fraction of the sky is accessible.

Feng shui (/ˈfʌŋˌʃuːi/ or /ˌfʌŋˈʃweɪ/), sometimes called Chinese geomancy, is a traditional form of geomancy that originated in ancient China. The term feng shui means, literally, "wind-water" (i.e., fluid). From ancient times, landscapes and bodies of water were thought to direct the flow of the universal qi – "cosmic current" or energy – through places and structures. More broadly, feng shui includes astronomical, astrological, architectural, cosmological, geographical, and topographical dimensions.

Historically, and in many parts of the contemporary Chinese world, feng shui has been used to determine the orientation of buildings, dwellings, and spiritually significant structures such as tombs.

The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac belt appear the Moon and the brightest planets, along their orbital planes. The zodiac is divided along the ecliptic into 12 equal parts, called "signs", each occupying 30° of celestial longitude. These signs roughly correspond to the astronomical constellations with the following modern names: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

The signs have been used to determine the time of the year by identifying each sign with the days of the year the Sun is in the respective sign. In Western astrology, and formerly astronomy, the time of each sign is associated with different attributes. The zodiacal system and its angular measurement in 360 sexagesimal degree (°) originated with Babylonian astronomy during the 1st millennium BC, probably during the Achaemenid Empire. It was communicated into Greek astronomy by the 2nd century BC, as well as into developing the Hindu zodiac. Due to the precession of the equinoxes, the time of year that the Sun is in a given constellation has changed since Babylonian times, and the point of March equinox has moved from Aries into Pisces.

The Islamic New Year (Arabic: رأس السنة الهجرية, Raʿs as-Sanah al-Hijrīyah), also called the Hijri New Year, is the day that marks the beginning of a new lunar Hijri year, and is the day on which the year count is incremented. The first day of the Islamic year is observed by most Muslims on the first day of the month of Muharram. The epoch (reference date) of the Islamic era was set as the year of the emigration of Muhammad and his followers from Mecca to Medina, known as the Hijrah, which equates to 622 CE in the Gregorian calendar. All religious duties, such as prayer, fasting in the month of Ramadan, and pilgrimage, and the dates of significant events, such as celebration of holy nights and festivals, are calculated according to the Islamic calendar. Hijri New Year is observed by 24 countries as a public holiday.

While some Islamic organizations prefer determining the new month (and hence the new year) by local sightings of the moon, most Islamic institutions and countries, including Saudi Arabia, follow astronomical calculations to determine future dates of the Islamic calendar. There are various schemas for calculating the tabular Islamic calendar (i.e. not based on observation), which results in differences of typically one or even two days between countries using such schema and those that use actual lunar sightings. For example, the Umm al-Qura calendar used in Saudi Arabia was reformed several times in recent years. The current scheme was introduced in 1423 AH (15 March 2002).

In astrology, planets have a meaning different from the astronomical understanding of what a planet is. Before the age of telescopes, the night sky was thought to consist of two similar components: fixed stars, which remained motionless in relation to each other, and moving objects/"wandering stars" (Ancient Greek: ἀστέρες πλανῆται, romanized: asteres planetai), which moved relative to the fixed stars over the course of the year(s).

To the Ancient Greeks who learned from the Babylonians, the earliest astronomers/astrologers, this group consisted of the five planets visible to the naked eye and excluded Earth, plus the Sun and Moon. Although the Greek term planet applied mostly to the five 'wandering stars', the ancients included the Sun and Moon as the Sacred 7 Luminaires/7 Heavens (sometimes referred to as "Lights",) making a total of 7 planets. The ancient Babylonians, Greeks, Persians, Romans, Medieval Christians, and others thought of the 7 classical planets as gods and named their 7 days of the week after them. Astrologers retain this definition of the 7 classical planets today.

In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. A dynamo is thought to be the source of the Earth's magnetic field and the magnetic fields of Mercury and the Jovian planets.

Marine navigation is the art and science of steering a ship from a starting point (sailing) to a destination, efficiently and responsibly. It is an art because of the skill that the navigator must have to avoid the dangers of navigation, and it is a science because it is based on physical, mathematical, oceanographic, cartographic, astronomical, and other knowledge.

Marine navigation can be surface or submarine.

Recessional velocity is the rate at which an extragalactic astronomical object recedes (becomes more distant) from an observer as a result of the expansion of the universe. It can be measured by observing the wavelength shifts of spectral lines emitted by the object, known as the object's cosmological redshift.

Astronomical rings (Latin: annuli astronomici), also known as Gemma's rings, are an early astronomical instrument. The instrument consists of three rings, representing the celestial equator, declination, and the meridian.

It can be used as a sun dial to tell time, if the approximate latitude and season is known, or to tell latitude, if the time is known or observed (at solar noon). It may be considered to be a simplified, portable armillary sphere, or a more complex form of astrolabe.

An astronomical clock, horologium, or orloj is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the Sun, Moon, zodiacal constellations, and major planets.

Khaṇḍakhādyaka (meaning "edible bite; morsel of food") is a Sanskrit-language astronomical treatise written by Indian mathematician and astronomer Brahmagupta in 665 CE. The treatise contains eight chapters covering such topics as the longitudes of the planets, diurnal rotation, lunar and solar eclipses, risings and settings, the moon's crescent and conjunctions of the planets. The treatise also includes an appendix which in some versions has only one chapter, and in other has three.

The treatise was written as a response to Aryabhata's Ardharatrikapaksa.

A supermoon is a full moon or a new moon that nearly coincides with perigee—the closest that the Moon comes to the Earth in its orbit—resulting in a slightly larger-than-usual apparent size of the lunar disk as viewed from Earth.‍ The technical name is a perigee syzygy (of the Earth–Moon–Sun system) or a full (or new) Moon around perigee.‍ Because the term supermoon is astrological in origin, it has no precise astronomical definition.‍

The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like earthquakes and volcanic eruptions, but no such link has been found.‍