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Астронет: Астрономическая картинка дня Солярография с аналеммами http://variable-stars.ru/db/msg/1304850/eng |
Credit & Copyright: Maciej Zapiór
and
Łukasz Fajfrowski
Explanation:
Today is the equinox.
The Sun crosses the celestial equator heading north at 16:57 UT, marking
the northern hemisphere's first day of spring.
To celebrate, consider this remarkable image following the Sun's
yearly trek through planet Earth's sky, the first
analemmas
exposed every day through the technique of
solargraphy.
In fact, three analemma curves were captured using a
cylindrical pinhole camera
by daily making three, separate, one minute long
exposures for a year,
from March 1, 2013 to March 1, 2014,
on a single piece of black and white photographic paper.
The well-planned
daily exposures began at 10:30, 12:00, and 13:30, CET
from a balcony looking south from the Kozanów district
in Wrocław, Poland.
That year's two equinoxes on March 20 and
September 22 correspond to
the
mid-points, not the cross-over points,
along the figure-8
shaped curves.
Apparent gaps in the curves are due to cloudy days.
Two solid lines at the lower left were both caused by a timer switch failure
that left the pinhole shutter open.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.