Credit & Copyright: Ian Griffin
(Otago Museum)
Explanation:
An analemma is
that figure-8 curve
you get when you mark the position
of the Sun at the same time each day for one year.
To make this one, a 4x5 pinhole
camera was set up looking north in
southern New Zealand skies.
The shutter was briefly opened each clear day in the afternoon at 4pm
local time exposing the same
photosensitized glass plate
for the year spanning September 23, 2022 to September 19, 2023.
On two days, the winter and summer solstices,
the shutter was opened again 15 minutes after the main
exposure and remained open until sunset to create the sun trails at
the bottom and top of the curve.
The equinox dates correspond to positions in the middle of the
curve, not the crossover point.
Of course,
the curve itself is inverted compared to an analemma traced
from the northern hemisphere.
And
while fall begins today
at the Autumnal Equinox for the northern hemisphere,
it's the Spring Equinox in the south.
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NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
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Публикации с ключевыми словами:
аналемма - Равноденствие
Публикации со словами: аналемма - Равноденствие | |
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