Observational astronomy

Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height.

A solstice is an astronomical event that occurs twice each year (in June and December) as the Sun reaches its highest or lowest excursion relative to the celestial equator on the celestial sphere.

The apparent magnitude (m) of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.

A space telescope or space observatory is an instrument located in outer space to observe distant planets, galaxies and other astronomical objects.

SKY-MAP.ORG (or WikiSky.org) is a wiki and interactive sky map that covers more than half a billion celestial objects.

A bolide (French via Latin from the Greek βολίς bolís, "missile") is an extremely bright meteor, especially one that explodes in the atmosphere.

A full moon is the lunar phase that occurs when the Moon is completely illuminated as seen from the Earth.

The cosmic microwave background (CMB) is the thermal radiation left over from the time of recombination in Big Bang cosmology.

Amateur astronomy is a hobby whose participants enjoy watching the sky, and the abundance of objects found in it with the unaided eye, binoculars, or telescopes.

In optics, an aperture is a hole or an opening through which light travels.

Nutation (from Latin nūtātiō, "nodding, swaying") is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behavior of a mechanism.

Zodiacal light is a faint, roughly triangular, diffuse white glow seen in the night sky that appears to extend up from the vicinity of the Sun along the ecliptic or zodiac.

Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the reflections.

Ultraviolet astronomy is the observation of electromagnetic radiation at ultraviolet wavelengths between approximately 10 and 320 nanometres; shorter wavelengths—higher energy photons—are studied by X-ray astronomy and gamma ray astronomy.

The airglow phenomenon was first identified in 1868 by Swedish physicist Anders Ångström.

The Astronomical Image Processing System (AIPS) is a software package to support the reduction and analysis of data taken with radio telescopes.

Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared (IR) radiation.

A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).

The sky (or celestial dome) is everything that lies above the surface of the Earth, including the atmosphere and outer space.

The International Astrophysical Observatory "GRANAT" (usually known as Granat; Russian: Гранат), was a Soviet (later Russian) space observatory developed in collaboration with France, Denmark and Bulgaria.

The history of X-ray astronomy begins in the 1920s, with interest in short wave communications for the U.

Compton scattering, discovered by Arthur Holly Compton, is the inelastic scattering of a photon by a charged particle, usually an electron.

In many cases astronomical phenomena viewed from the planet Mars are the same or similar to those seen from Earth but sometimes (as with the view of Earth as an evening/morning star) they can be quite different.

A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum.

Explorer 10 (also known as Explorer X or P14) was an American Earth-orbital satellite that investigated Earth's magnetic fields and nearby plasma.

In astronomy, air mass (or airmass) is the optical path length through Earth’s atmosphere for light from a celestial source.

Theoretical astronomy is the use of the analytical models of physics and chemistry to describe astronomical objects and astronomical phenomena.

In astronomy a phase curve describes the brightness of a reflecting body as a function of its phase angle.

In physics, optical depth or optical thickness, is the natural logarithm of the ratio of incident to transmitted radiant power through a material, and spectral optical depth or spectral optical thickness is the natural logarithm of the ratio of incident to transmitted spectral radiant power through a material.

The ecliptic coordinate system is a celestial coordinate system commonly used for representing the positions and orbits of Solar System objects.