Change of brightness during Annular Solar Eclipse (May 21, 2012)

Date & Time: May 21 2012
Program mode (spot integral)
Optical: SIGMA f=4.5mm EX Circular DC
Fixed on tripod
Digital Camera: Nikon D80 (Remodeled)
Location: Kujihama, Hitachi city, Ibaraki pref.

Camera Settings: Recording format...JPEG-FINE (3872 x 2592)
CCD Sensitivity...ISO200, White-Balance...Manual

Change of sky brightness during Annular Eclipse

Individual numbers correspond to those in upper image.
A white curve indicates calculated LV under an assumption that the illuminance is proportion
to the area ratio of uneclipsed solar area with the limb-darkening effect
(Assumed the LV of normal midday sky, LV0, increases linearly from 15 to 16.5).

This multi-flame picture has captured change of sky brightness in progress of Annular solar eclipse with an SLR digital still camera and whole-sky photo lens in program mode. Individual images have been adjusted their brightness in proportion to the Light-Values (LVs) to record sky of zenith with definite photographic density. A figure indicates the change of LVs with an interval of a minute, you can confirm that LV was down about 3 or 4 steps during annular eclipse, estimated the brightness (illuminance) of sky was about one eighth to sixteenth of that in normal midday.
Our naked eyes can adapt to some changes of brightness, I could not recognize such a drastic change. But we can notice the darkness during annular eclipse by comparing these images. The area of sun in maximum eclipse was about 7.9% of that without eclipse in this time, the intensity of solar radiation was about one 12.6th. This value almost agrees with decreased amount of LV.

Time change of Baily's beads

Total lunar eclipse (Feb 9, 1990)

Copyright(c) 2012 by Naoyuki Kurita, All rights reserved.
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