Terms and abbreviations

Aberration of light

A small change of apparent direction caused by observer motion combined with the finite speed of light. It is distinct from the star’s own proper motion.

Altitude

The angle of an object above or below the horizon. It is a different quantity from the observing site's height above sea level.

Also known as: elevation angle

Apparent magnitude

A scale describing how bright an object appears to us. Smaller, including negative, values mean brighter objects; the number alone does not determine weather or naked-eye visibility.

Arcminute

One sixtieth of a degree, used for angular sizes, distances and differences. It is not a minute of time. One arcminute contains sixty arcseconds.

Also known as: arcmin

Astrometry

The branch of astronomy concerned with measuring celestial positions and motions. It directly informs validation of positions shown on a sky map.

Astronomical Data Query LanguageADQL

A SQL-based language defined for querying astronomical data. It includes astronomy-specific spatial operations and is not assumed to be directly supported by every database.

Also known as: catalog query

Astronomical unitAU / AB

A length unit useful for Solar System distances, defined as exactly 149,597,870,700 metres. The instantaneous Earth–Sun distance is not always one astronomical unit.

Atmosphere

The layer of gas around a planet; on Earth it scatters daylight. This application's atmosphere layer is a day/night visual simulation, not measured weather.

Atmospheric refraction

Bending of light in the atmosphere changes an object's apparent altitude. A standard-atmosphere model is not a measurement of actual weather; the effect matters especially near the horizon.

Also known as: refraction

Azimuth

The angle describing an object's direction along the horizon. It is interpreted using the map's stated reference direction and angular unit.

Also known as: horizontal direction

Azimuthal grid

Lines of direction and altitude relative to the observer. Azimuth starts at north and increases toward east; altitude is measured from the mathematical horizon.

Compass

A tool that obtains a heading from Earth’s magnetic field or device orientation sensors. Its north reference may differ from geographic north.

Compass calibration

The process of assessing and correcting a heading offset. Device sensor calibration and alignment to a known true map direction are different; alignment does not remove measurement uncertainty.

Conjunction

Alignment at a defined celestial direction or longitude. Inferior and superior conjunctions are distinguished for inner planets; alignment does not mean physical contact.

Constellation

A named region of the sky. Connected-star figures are schematic aids; their stars need not be near each other in physical space.

Constellation art

An illustration of a cultural figure associated with a constellation. It is neither a celestial photograph nor an IAU boundary; it is anchored to star positions.

Coordinated Universal TimeUTC

A time scale used as a common reference for time information. It differs from local civil time; astronomical calculations can require conversion to other time scales.

Also known as: coordinated time

DeclinationDec

The angular coordinate north or south of the celestial equator, expressed in degrees. It is not the same datum as an observing site's terrestrial latitude.

Deep-sky objectDSO

A general term for targets such as galaxies, star clusters and nebulae outside the Solar System. A map marker does not imply naked-eye visibility.

Ellipsoidal height

A point’s height in metres relative to a reference ellipsoid for Earth. It differs from height above mean sea level; conversion needs a suitable geoid model and datum. Yorungez does not convert it automatically; leave unknown values empty.

Also known as: ellipsoid height, GPS height, geoid, datum

Elongation

The angular separation of an object from the Sun as seen from Earth. Greatest elongations of Mercury and Venus are calculated calendar events; observability still depends on location and conditions.

Ephemeris

A table or computed data set describing celestial objects at specified times. Its reference frame and time scale are part of its interpretation.

Also known as: ephemerides

Equatorial grid

Lines of right ascension and declination based on the celestial equator. Yorungez uses a J2000 grid transformed into the horizontal view for the observer and instant.

Equinox

The instant when the Sun’s apparent path crosses the celestial equator. March and September equinoxes are global instants; the seasonal name depends on hemisphere.

Flexible Image Transport SystemFITS

A scientific file format for astronomical images, tables and other data, accompanied by descriptive header metadata.

Also known as: astronomical file format

Global Positioning SystemGPS

A satellite-based positioning system. Browser location may also use other methods available on the device; the reported accuracy is considered separately.

Also known as: device location, positioning

Greenwich Mean TimeGMT

A historical time name associated with the Greenwich meridian, also used in offset labels such as GMT+03:00. In astronomy this display label does not make UTC instants, UT1 and TT interchangeable.

Hierarchical Equal Area isoLatitude PixelizationHEALPix

A hierarchical, equal-area pixelization of the sphere, useful for partitioning and indexing large sky data sets.

Also known as: spherical pixelization

Hierarchical Progressive SurveysHiPS

A multiresolution scheme for progressively serving sky survey data at different zoom levels.

Also known as: sky surveys

IANA time zoneIANA

A regional identifier such as Europe/Istanbul. It selects date-dependent UTC offsets and daylight-saving rules, unlike a fixed GMT offset.

Illustrative landscape

A visual landscape supporting the observer's sense of ground and horizon. This open field is not measured terrain or obstacles at the real location and does not change celestial calculations.

J2000.0 referenceJ2000.0

A standard reference used to interpret celestial coordinates and catalogue epochs. This catalogue starts at J2000.0 while the sky map is recalculated for the selected instant.

Light pollution

The effect of artificial light on the night environment and the appearance of the sky. It can affect observing conditions and is assessed separately from whether an object is geometrically above the horizon.

Also known as: sky glow

Light-year

The distance light travels in vacuum in one Julian year. It is a distance unit, not a duration, equal to about 9.46 trillion kilometres.

Local time

The display of a UTC instant using a selected region's time-zone rules. Changing region or language preserves the actual instant. Daylight-saving changes can skip or repeat local clock times.

Location accuracy

The device-reported positional uncertainty, retained in metres with its measurement time. More decimal digits or manually picking a map point do not guarantee better physical accuracy.

Magnetic north

The north direction indicated by a compass following the local magnetic field. Its difference from geographic north varies with place and time and must not be assumed corrected.

Moon phase

How the sunlit Moon appears from Earth. New Moon, first quarter, full Moon and last quarter are primary phases; a phase instant is global, while being above the horizon depends on location.

Opposition

A superior planet lying opposite the Sun in ecliptic longitude as viewed from Earth. The date alone does not establish weather conditions or naked-eye visibility.

Parallax

An apparent positional shift caused by a change of viewpoint. Earth’s annual motion produces a small shift for nearby stars.

PostgreSQL Geospatial ExtensionPostGIS

Adds storage, indexing and querying of geospatial data. Yorungez can consider it for future observing-site and environmental analysis on Earth; core sky calculations do not require it.

Also known as: geographic information system, GIS

PostgreSQL Spherical Geometry ExtensionpgSphere

An extension adding spherical objects and operations to PostgreSQL. It can support celestial-coordinate queries, but is not a planetary ephemeris engine.

Also known as: spherical geometry

Proper motion

The change in a star’s sky position relative to distant stars over time. It is included when carrying a catalogue position to another year.

Quad Tree CubeQ3C

A PostgreSQL extension for fast spatial querying and cross-matching of positions on a sphere, considered when advanced catalog queries are needed.

Also known as: cone search

Right ascensionRA

A position coordinate measured along the celestial equator, commonly expressed in hours. It is distinct from terrestrial longitude; its reference frame and epoch must be specified.

Rise and set

The upward or downward crossing of a defined horizon. This timeline uses standard atmospheric refraction and the Sun/Moon upper limb; local mountains, buildings and weather are not evaluated.

Solstice

The instant when the Sun reaches its northernmost or southernmost position relative to the celestial equator. The summer/winter meaning of June and December solstices depends on hemisphere.

Table Access ProtocolTAP

A protocol for accessing table data and metadata through a service, including astronomical catalogs. ADQL queries are one supported form of access.

Also known as: table service

Topocentric position

A position calculated for the selected observing site rather than the centre of Earth. Observer location is especially relevant for nearby objects such as the Moon.

Also known as: observer-centred

True north

The direction toward the geographic North Pole, at the northern end of Earth’s rotation axis. The sky map measures azimuth from this north.

Twilight

The period when the atmosphere remains illuminated while the Sun is below the horizon. Different twilight types are defined by the Sun’s centre depression below the horizon.

World Coordinate SystemWCS

Information mapping image pixels to physical coordinates such as positions on the sky. Here world coordinates are not restricted to locations on Earth.

Also known as: pixel sky coordinates