Photo of the Day: Star Wars by Justeline
“A different kind of star trails made with the gradual defocusing technique which allows the differences in the colors (and thus the temperature) of the stars to be appreciated in a visual way. Cameras normally can’t record the true color of the stars because the range of brightness of the stars in the sky exceeds the dynamic range of any photographic film, or camera sensor. By gradually stepping more and more out of focus during the star trail shot, there comes a time when the intensity is spread out enough so that the true color of the star can be recorded.
For this image 25 two minute shots (f/4, ISO 400, 1sec interval) were taken while the lens was slightly defocused in every shot. Later they were all stacked together in “lighten” blending mode over a base shot taken earlier, during twilight.
For those of you wanting to decode the stars by their color, here’s the “key”:
BLUE SUPERGIANT - Bluish, temperature about 30,000 ° C
BLUE GIANT - temperature about 15,000 ° C
WHITE STAR -temperature about 9,000 ° C
YELLOWISH-WHITE STAR - temperature about 7,000 ° C
YELLOW STAR -temperature about 5,500 ° C
ORANGE STAR -temperature about 4,000 ° C
RED DWARF - temperature about 3,000 ° C”
(Source: photoradar.com)
