A
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.
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, 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.
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.
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.
Angular path that stars rotate about a celestial pole (north, south) during the exposition time.
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.
B
Period of twilight where there is neither full daylight nor complete darkness, and light takes a strong blue color. The moment is considered special because of the quality of light. PhotoPills considers the blue hour as the time, both morning and evening, when the center of the sun is between 4º and 6º below the horizon (-4º,-6º). Learn more on Wikipedia.
C
Morning civil twilight begins when the geometric center of the sun is 6º below the horizon (-6º), civil dawn, and ends at sunrise. Evening civil twilight begins at sunset and ends when the geometric center of the sun reaches 6° below the horizon (-6º), civil dusk. Learn more on Wikipedia.
The projection of the Earth's equator out into space. At the Celestial equator, stars seem to travel in a straight line. Learn more on Wikipedia.
A star that, as viewed from a given latitude on Earth, never sets (that is, never disappears below the horizon), due to its proximity to one of the celestial poles. Learn more on Wikipedia.
The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere. Learn more on Wikipedia.
Instrument for determining directions (azimuth), as by means of a freely rotating magnetized needle that indicates magnetic north. Learn more on Wikipedia.
The ratio of the sensor format relative to a 35 mm frame. Learn more on Wikipedia.
It is the largest on-film/sensor circle that you can see as a well defined point on an 8''×10'' print when viewed at from a "normal" viewing distance of 2 to 3 feet. Anything larger is seen as a small circle, not a point and is therefore perceived as out of focus. Learn more on Wikipedia.
The desired length of the video clip that portrays the event.
D
Distance between a location (or a point on the Earth's surface) and the apparent line that separates earth from sky (horizon). Learn more on Wikipedia.
The number of daylight hours per day. Refers to the time measured from the moment the upper limb of the sun's disk appears above the horizon during sunrise to the moment when the upper limb disappears below the horizon during sunset. Learn more on Wikipedia.
It is the distance between the sun or the moon and the Earth.
The distance between the farthest and nearest points which are in acceptable focus. This can also be identified as the zone of acceptable sharpness in front of and behind the subject to which the lens is focused on. Learn more on Wikipedia.
Depth of Field near limit. Distance from where acceptable focus starts, when you focus at a given distance.
Depth of Field far limit. The distance where acceptable focus ends, when you focus at a given distance.
Distance between the DoF Near Limit and the focus plane.
Distance between the focus plane and the DoF Far Limit.
Angle of view measured diagonally (from one corner of the frame to its opposite corner).
Field of view measured diagonally (from one corner of the frame to its opposite corner).
The vertical angular distance between the center of a celestial body and the celestial equator. You can measure it using PhotoPills Night AR or PhotoPills Planner Night AR. A declination of +20° means that the celestial body is located 20° north of the celestial equator. The south polar cap is at a declination of –90°, the equator is at declination 0°, and the north polar cap is at a declination of +90°. Declination is to a celestial globe as latitude is to a terrestrial globe, a vertical positioning of an object. Learn more on Wikipedia.
E
The vertical angular distance between a celestial body (sun, moon, ...) and the observer's local horizon. For visible objects it is an angle between 0 degrees to 90 degrees. For example, the elevation of the sun is the angle between the direction of the geometric center of the sun's apparent disk and the observer's (idealized) horizon. We say sun is at elevation 12º when it is situated at 12º above our ideal horizon. Learn more on Wikipedia.
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).
Occurs twice a year (around 20 March and 22 September), when the tilt of the Earth's axis is inclined neither away from nor towards the sun, the center of the sun being in the same plane as the Earth's equator. Learn more on Wikipedia.
The amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph. Learn more on Wikipedia.
A number representing equivalent shutter speeds and lens apertures combinations for the same exposure, given a scene brightness. At ISO 100, 0 represents (f/1.0 at 1 sec); 1 = (f/1.4 at 1 sec) or (f/1.0 at 1/2 sec); 2 = (f/2.0 at 1 sec) or (f/1.4 at 1/2 sec) or (f/1.0 at 1/4 sec) and so on. Learn more on Wikipedia.
Exposure value at ISO 100.
Total time of the event for which you want to create a time-lapse video.
F
This phase occurs when one-half of the moon is illuminated by direct sunlight. The illuminated part is increasing. The moon squares the sun. Learn more on Wikipedia.
This phase occurs when the visible moon is fully illuminated by direct sunlight. At the full moon, the sun and moon are in opposition. Learn more on Wikipedia.
International sequence of numbers, expressing relative aperture, i.e. lens focal length divided by effective aperture diameter. Each change of f-setting halves or doubles image brightness. Learn more on Wikipedia.
The measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. Learn more on Wikipedia.
Transparent lens attachment used to modify the light coming into a lens, to change the color, or other characteristics of an image. They are used both on the camera and in the darkroom. Learn more on Wikipedia.
The distance (in mm) from the optical center of the lens to the focal plane. Learn more on Wikipedia.
What is visible through the camera-lens combination at a particular position and orientation in space. Objects outside the FOV when the image is made are not captured.
Field of view is expressed in linear measurements (meters, mm; feet, inches) for a given working distance. Learn more on Wikipedia.
It refers to the focal length needed to match horizontal or vertical angle of view.
The number of frames per second in your video. For example, if you have selected 25 fps you will need 25 photographs to generate one second of video. Learn more on Wikipedia.
G
Greenwich Mean Time (GMT) is a time system originally referring to mean solar time at the Royal Observatory in Greenwich, London. For example, GMT-4 means that Standard Time is 4 hours behind of Greenwich Mean Time. New York City uses GMT-4 as its Time Zone. Learn more on Wikipedia.
The time of day when the sun is low in the sky, producing a soft, diffused light which is much more flattering than the harsh midday sun. This type of light produces less contrast, reducing the chances of losing parts of your subject in strong shadows or blown-out highlights. The warm glow adds a pleasing feel to the scene, and the long shadows help to pick out details, adding texture and depth to the image. PhotoPills considers the golden hour as the time, both morning and evening, when the center of the sun is between 6 degrees above the horizon and 4 degrees below the horizon (6º,-4º). Learn more on Wikipedia.
H
The apparent line that separates earth from sky. Learn more on Wikipedia.
The vertical distance of an object or location above the horizon level. PhotoPills uses Height Above Horizon to adjust the calculations of sun and moon rise and set times. For example, an observer situated at the top of a mountain at 2.000 feet of height above his horizon will see sunrise earlier in the morning than another observer situated at the horizon level.
The closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp. Learn more on Wikipedia.
It is situated at half the hyperfocal distance. If we focus at the hyperfocal distance, we'll get sharpness from the Hyperfocal Near Limit to infinity.
Angle of view measured horizontally (from the left to right edge of the frame).
Field of view measured horizontally (from the left to right edge of the frame).
I
Instrument for measuring angles of slope (or tilt), elevation or depression of an object with respect to gravity. Learn more on Wikipedia.
The abbreviation of International Organization for Standardization. It is a scale to measure Film speed. Learn more on Wikipedia.
The size in Megabytes (MB) of an image file.
J
K
L
This phase occurs when one-half of the moon appears illuminated by direct sunlight. The illuminated part is decreasing. The moon squares the sun. Learn more on Wikipedia.
A geographic angular coordinate that specifies the north-south position of a point on the Earth's surface. Learn more on Wikipedia.
A geographic angular coordinate that specifies the east-west position of a point on the Earth's surface, from the prime meridian at Greenwich, England. Learn more on Wikipedia.
M
The only natural satellite of the Earth. Learn more on Wikipedia.
New moon, Waxing Crescent , First Quarter, Waxing Gibbous, Full moon, Waning Gibbous, Last Quarter and Waning Crescent. Learn more on Wikipedia.
The instant at which the upper edge of the moon appears on the horizon. Moonrise occurs before the moon actually reaches the horizon because the moon's image is refracted by the Earth's atmosphere.
The instant at which the upper edge of the moon disappears bellow the horizon. Moonset occurs after the upper edge of the Moon actually reaches the horizon because the moon's image is refracted by the Earth's atmosphere.
The spiral galaxy containing our solar system. Visible from the Earth as a broad band of faint light in the night sky. Learn more on Wikipedia.
Photo print size.
It is the minimum distance between you and the subject you want to fit in the frame. It varies with camera sensor, focal length, object dimensions and camera orientation.
Declination of the stars situated the furthest from the celestial pole that fit in our frame. These stars need a shorter exposure time to appear as Spots in our photo. You can estimate the Minimum Star Declination using PhotoPills Night AR or PhotoPills Planner Night AR. Learn more on Wikipedia.
Maximum exposure time that all stars appear as bright spots in our photo.
N
This phase occurs when the moon lies between the sun and the Earth. The side facing the sun is sunlit, while the side facing the Earth is not lit by the sun. This alignment leaves the moon dark and invisible to us. Learn more on Wikipedia.
Nautical twilight, both morning and evening, is the time when the center of the sun is between 6° and 12° below the horizon (-6º,-12º). In general, nautical twilight ends when navigation via the horizon at sea is no longer possible. Learn more on Wikipedia.
The half of the Earth that is north of the equator. Learn more on Wikipedia.
Number of photos we need to take during the event to create a time-lapse video.
O
Anything that can hide the sun/moon: a mountain, a hill, a building.
Angle centered on the Observer's pin location and measured between the direction of the Obstacle's pin and the north.
P
Commonly North Star, Northern Star or Pole Star, is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star. Learn more on Wikipedia.
The point in an object's orbit when it is the closest to the Earth. Super moons or moon perigees are particularly useful in photography. Full moons that occur on the perigee side of the moon's orbit seem extra big and bright. The best time to look is when the moon is near the horizon. For reasons not fully understood by astronomers or psychologists, low-hanging moons look unnaturally large when they beam through trees, buildings and other foreground objects. Learn more on Wikipedia.
Q
R
Formula to calculate maximum exposure time to capture Stars as Spots that take into account Sensor Size, Focal Length and Minimum Star Declination. You can estimate the Minimum Star Declination using PhotoPills Night AR or PhotoPills Planner Night AR.
Fast way to estimate the maximum exposure time to obtain stars as spots. It's value is obtained by dividing 500 by the focal length.
S
The ratio of an object’s height to its shadow length. Multiply the height of any object by the shadow ratio to calculate the length of the object's shadow.
The star at the center of the Solar System. Learn more on Wikipedia.
The instant at which the upper edge of the sun appears on the horizon in the morning. In fact, sunrise occurs before the sun actually reaches the horizon because the sun's image is refracted by the Earth's atmosphere. Learn more on Wikipedia.
The instant at which the upper edge of the sun disappears below the horizon in the evening. Sunset occurs after the upper edge of the sun reaches the horizon because the sun's image is refracted by the Earth's atmosphere. Learn more on Wikipedia.
When taking a long exposure photo of the stars in the nighttime sky using a camera on a fixed mount, a star trail is the line of light recorded on the photographic medium caused by the rotation of the Earth during the period of time when the camera's shutter is held open. Learn more on Wikipedia.
An astronomical event that happens twice each year as the sun reaches its highest or lowest excursion relative to the celestial equator on the celestial sphere. As a result, on the day of the solstice the sun appears to have reached its highest or lowest annual altitude in the sky above the horizon at local solar noon. Learn more on Wikipedia.
The coincidence of a full moon with the closest approach the moon makes to the Earth on its elliptical orbit (perigee), resulting in the largest apparent size of the moon's disk as seen from Earth. Learn more on Wikipedia.
The effective length of time a camera's shutter is open. Learn more on Wikipedia.
A method of estimating correct daylight exposures without a light meter. The basic rule is, "On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight. For example; On a sunny day and with ISO 100 film / setting in the camera, one sets the aperture to f/16 and the shutter speed to 1/100. Learn more on Wikipedia.
The distance between the lens of a camera and a subject being photographed.
Height of the subject you want to fit in the frame.
Width of the subject you want to fit in the frame.
The part of the Earth that lies south of the equator. Learn more on Wikipedia.
Time between two consecutive shots or frames during the Event. A longer interval will result in a shorter, faster running video.
T
It is the remaining time to sunset or moonset.
The time the sun or the moon is at azimuth 180º (south), and it's at its maximum elevation.
It is the remaining time to sunrise or moonrise.
A secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens. Learn more on Wikipedia.
It helps you estimate the size or number of memory cards you will need to save all the photos of your time-lapse video.
Technique whereby the frequency at which film frames are captured (the frame rate) is much lower than that used to view the sequence. When played at normal speed, time appears to be moving faster and thus lapsing. For example, an image of a scene may be captured once every second, then played back at 30 frames per second. The result is an apparent 30-times speed increase. Learn more on Wikipedia.
U
V
Distance between you and your visible horizon.
Distance you are viewing the photo.
Clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain. 20/20 vision is 6/6 vision. At 20 feet or 6 meters, a human eye with nominal performance is able to separate lines that are one arc minute apart (equivalent to lines that are spaced 1.75 mm apart). Learn more on Wikipedia.
Angle of view measured vertically (from the top to bottom of the frame).
Field of view measured vertically (from the top to bottom of the frame).
W
This phase occurs when the visible moon is partly but less than one-half illuminated by direct sunlight. The illuminated part is increasing. Learn more on Wikipedia.
This phase occurs when the moon is more than one-half but not fully illuminated by direct sunlight. The illuminated part is increasing. Learn more on Wikipedia.
This phase occurs when the moon is partly but more than one-half illuminated by direct sunlight. The illuminated part is decreasing. Learn more on Wikipedia.
This phase occurs when the moon is partly but less than one-half illuminated by direct sunlight while the illuminated part is decreasing. Learn more on Wikipedia.
X
Y
Z
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