Observational astronomy

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.

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.

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

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

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

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

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

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.

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.

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

(For the view from above the astronomical object's surface, see Extraterrestrial atmospheres.) In astronomy, the term extraterrestrial sky refers to a view of outer space from the surface of a world other than Earth.

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

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

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

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.

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

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.

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.

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

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.

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

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.

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