keogram
Sign in to savethumb|right|alt=A keogram (below) showing the plot (graphics)|plot based on the marked slice of the images (above) taken by the camera. |A keogram (below) showing the plot based on the marked slice of the images (above) taken by the camera. A keogram ("keo" from "Keoeeit" – Inuit word for "Aurora Borealis") is a way of displaying the intensity of an auroral display over time. It creates a time-dependent graph by taking a narrow slice of a series of images recorded by a camera, more specifically and ideally a "whole sky camera". Keograms are usually created from a north-south oriented slice of
Described at
APOD: 2022 March 21 - The Sky in 2021
A different astronomy and space science related image is featured each day, along with a brief explanation.
apod.nasa.gov →Explanation: What if you could see the entire sky -- all at once -- for an entire year? That, very nearly, is what is pictured here. Every 15 minutes during 2021, an all-sky camera took an image of the sky over the Netherlands . Central columns from these images were then aligned and combined to create the featured keogram , with January at the top, December at the bottom, and the middle of the night running vertically just left of center. What do we see? Most obviously, the daytime sky is mostly blue , while the nighttime sky is mostly black. The twelve light bands crossing the night sky are caused by the glow of the Moon . The thinnest part of the black hourglass shape occurs during the summer solstice when days are the longest, while the thickest part occurs at the winter solstice . Yesterday was an equinox -- when night and day were equal -- and the northern-spring equinox from one year ago can actually be located in the keogram -- about three-quarters of the way up.
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- Keogram of aurora September 7-8, 2021.jpg
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- Keogram
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thumb|right|alt=A keogram (below) showing the plot (graphics)|plot based on the marked slice of the images (above) taken by the camera. |A keogram (below) showing the plot based on the marked slice of the images (above) taken by the camera. A keogram ("keo" from "Keoeeit" – Inuit word for "Aurora Borealis") is a way of displaying the intensity of an auroral display over time. It creates a time-dependent graph by taking a narrow slice of a series of images recorded by a camera, more specifically and ideally a "whole sky camera". Keograms are usually created from a north-south oriented slice of the images, with north at the top in the Northern Hemisphere and south at the top in the Southern Hemisphere. This allows one to easily see the general activity of the display that night, interruptions by clouds, and the regions in which the aurora was seen in terms of latitude.
The use of keograms started in the 1970s by Eather et al. to allow a more practical and efficient way of determining the activity of the aurora throughout the recorded night and provide a view of the movements of it. Cameras can also record in wavelengths outside of the human visible spectrum. Thus, keograms can also be used to analyse the conditions of the equatorial plasma bubbles (EPB) in the ionosphere of the Earth, to estimate its zonal drift.