Augmented Reality (AR)

A generation of a composite view for the user that is the combination of the real scene viewed by the user and a virtual scene generated that augments the scene with additional information. For example, PhotoPills allows you to visualize moon position and moon path information on the real scene. Learn more on Wikipedia.


The angle between a celestial body (sun, moon, …), measured clockwise around the observer's horizon, and the North. It determines the direction of the celestial body. So a celestial body due North has an azimuth of 0°, one due East 90°, South 180° and West 270°. For example, sun is at azimuth 193º when it is situated at 193º measured clockwise from North. Learn more on Wikipedia.

Azimuth error

When looking for dates and times the sun or moon will be in a desired position, the error of the azimuth and elevation define the spatial region we consider results to be acceptable. By introducing a margin of maneuver when setting the desired sun or moon's position (azimuth, elevation), likelihood of getting a result increases. To sum up, the Planner will give us any date and time sun or moon will be at: (azimuth+-error, elevation+-error). For example if we are looking for dates when the moon is at azimuth 93º and elevation 10º and we accept a 3º azimuth error and 2º elevation error. We will get as a result  all dates in which the moon's azimuth will be in the interval (90º,96º) and the moon's elevation will be in the interval (8º,12º).


The height of an object (or a point on the Earth's surface) above sea level. Learn more on Wikipedia.

Astronomical Twilight

Astronomical twilight, both morning and evening, is the time when the center of the sun is between 12° and 18° below the horizon (-12º,-18º). From the end of astronomical twilight in the evening to the beginning of astronomical twilight in the morning, the sky is dark enough for all astronomical observations. Learn more on Wikipedia.

Age (Moon)

The time that has elapsed since the last preceding conjunction of the sun and moon (new moon).


The point in an object's orbit when it is the furthest from the Earth. Learn more on Wikipedia.


The adjustable opening in a camera lens that -like an eye's iris- controls the amount of light that reaches the film or digital sensor. The size of such aperture is called the f-stop, like f/2.8 Learn more on Wikipedia.

Angle of View (AoV)

The total angular field if view in front of a lens with a given focal length of a camera with a given film or sensor format. Learn more on Wikipedia.

Angle (Star Trail)

Angular path that stars rotate about a celestial pole (north, south) during the exposition time.

Angular diameter (sun, moon)

The angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. The angular diameter of the Sun and Moon are almost the same, as seen by an observer on Earth, aproximately: 0.5º. Learn more on Wikipedia.