The open star cluster NGC 457 ("Owl cluster", "ET cluster") in the constellation Cassiopeia
on December 19 / 20, 2015. NGC 457 is 9000 light-years from Earth, measures 30 light-years in diameter and was discovered by the William Herschel
1787 (source: Wikipedia).
Twenty-two exposures of approximately 3 minutes at ISO 400 with no dark frame subtraction were stacked with Deep Sky Stacker
(resulting in a 1 h 8 min exposure) and further processed in Photoshop.
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Equipment: Canon EOS 450D Baader modified camera, TeleVue Paracorr Type II coma corrector,
16" f/4.5 "Ninja" dobsonian telescope riding on a dual-axis Tom Osypowski equatorial platform,
Lacerta MGEN autoguider, Lacerta off axis system (field of view comparison:
image of the moon with the same equipment).
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