Observational astronomy

thumb|upright=1.5|The eight planets of the Solar System with size to scale (up to down, left to right): [[Saturn, Jupiter, Uranus, Neptune (outer planets), Earth, Venus, Mars, and Mercury (inner planets)]] A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets by the most restrictive definition of the term: the terrestrial planets Mercury, Venus, Earth, and Mars, and the giant planets Jupiter, Saturn, Uranus, and Neptune. The best available theory of plane

upright=1.25|thumb|The night sky over Slovenia in July upright=1.25|thumb|cirrus cloud|Cirriform clouds and a quarter [[Moon in the blue daytime sky over Germany]]

lunar phase: completely illuminated disc

thumb|A Prism (optics)|prism separates white light by dispersing it into its component colors, which can then be studied using spectroscopy.

electromagnetic radiation as a remnant from an early stage of the universe in Big Bang cosmology

shape of the sunlit portion of the Moon as viewed from Earth

measure of brightness for celestial objects, as seen from Earth

logarithmic measure of the luminosity of a celestial object

anthropogenic light in the night environment, caused by excess or misdirected lighting

subfield of astronomy that studies celestial objects at radio frequencies

glow in the night sky appearing to extend from the Sun's direction and along the zodiac

thumb|200px|In this July 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation.

situation where two celestial bodies are on opposite sides of the sky, viewed from a given place (usually Earth)

logarithmic measure of the brightness of an astronomical object

scattering of a photon off of a charged particle

phenomenon in astronomy

the determination of light intensities of astronomical bodies, including stars

thumb|Different apertures of a lens thumb|In biology, the pupil (appearing as a black hole) of the eye is its aperture and the iris is its diaphragm. In humans, the pupil can constrict to as small as 2 mm (8.3) and dilate to larger than 8 mm (2.1) in some individuals. thumb|A camera aperture thumb|Definitions of Aperture in the 1707 Glossographia Anglicana Nova thumb|Aperture icon

observational astronomy of emissions over the wavelength band 0.75 to 300 micrometers

branch of astronomy that uses X-ray observation

thumb|upright=1.5|Comparison of photometric and radiometric quantities Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which characterize the light's interaction with the human eye.

field of astronomy concerned with recording data about the observable universe

practice of engaging in visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"

in astronomy, the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer

science of temporal, spatial, and spectral distributions of radiation

thumb|Airglow over Auvergne, France thumb|Yellow, green and red bands of airglow along Earth's limb as seen from space.

observational astronomy performed at less than 10 nm wavelengths

multi-spectral imaging and spectroscopic redshift survey

any astronomical object that is not an individual star

deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere

Rising of stars prior to sunrise

thumb|right|220px|Saturn's moon Mimas is lit by Saturnshine on the right and sunshine at the top. thumb|right|220px|The Moon lit by [[earthshine, captured by the lunar-prospecting Clementine spacecraft in 1994. Clementine's color enhanced image reveals (from right to left) the Moon lit by earthshine, the Sun's corona rising over the Moon's dark limb, and the planets Saturn, Mars, and Mercury (the three dots at lower left).]]

thumb|300px|The gegenschein appears in this image as a bright spot on the diagonal band (running top left to lower right) above the Very Large Telescope. (The [[Andromeda Galaxy and Pleiades are prominent in the lower half of the image.)]]

Exceptionally bright comets

thumb|The twinkling of the brightest star in the [[night sky Sirius (apparent magnitude of −1.1), shortly before upper culmination at the meridian, at 20° above the southern horizon. In 29 seconds, Sirius appears to move 7.5 arcminutes from left to right.]] thumb|Comparison of twinkling of a star (top) and a planet (bottom). The turbulent atmosphere (shaded blue) distorts their wavefronts (cyan lines) differently with time, like caustics on a swimming pool floor. When a dark part hits the observer (white circle), the object appears dark, and vice versa. An object with larger angular size smear

measure of brightness of an astronomical object

dark sky in the deep twilight or at night

short-lived light, color, or change in appearance on the surface of the Moon

amount of apparent blurring and twinkling of astronomical objects due to atmospherical effects

aspect of a heavenly body in which it makes a right angle with the direction of the Sun

astronomical observation via telescopes using visible light

number of meteors a single observer would see in an hour of peak activity for the meteor shower

Astronomical instrument used to measure movements or variations in the brightness of celestial objects

Sky-Map.org (or WikiSky.org) is a wiki and interactive sky map that covers over half a billion known celestial bodies. WikiSky is designed, in part, as a wiki. Users can edit information about different stars by writing articles, adding Internet links, uploading images, or creating a special interest group for a specific task.

measurement relating to observed visual binary stars

type of astronomy involving observation of gravitational waves

general map or image of a region of the sky with no specific observational target

reflective and observational astronomy that uses radar to map the surfaces of bodies in the solar system

albedo subtype

The International Astrophysical Observatory "GRANAT" (usually known as Granat; , lit. pomegranate), was a Soviet (later Russian) space observatory developed in collaboration with France, Denmark and Bulgaria. It was launched on 1 December 1989 aboard a Proton rocket and placed in a highly eccentric four-day orbit, of which three were devoted to observations. It operated for almost nine years.

brightening of a rough surface, when illuminated from directly behind the observer

cosmology

light whose rays are parallel, and therefore will spread minimally as it propagates

purported correlation of the cosmic microwave background with the Earth’s ecliptic

astronomy database

period of time during which a planet's surface reflects specific amounts of sunlight from the perspective of a given point in space

greater measured infrared flux than expected from star temperature

Variations of lighting of the planet's surface

study of astronomical objects that release ionizing radiation of highly energetic wavelengths

What an observer on Mars can see in the sky