The variable nebula NGC 2261 ("Hubble's Variable Nebula") in the constellation Monoceros
on December 19 / 20, 2015. NGC 2261 is 2500 light-years from Earth, one light-year across and is illuminated by the star R Monocerotis, the
bright T Tauri variable star at the left end of the nebula in the image above. Dense condensations of dust near the star cast shadows out into
the nebula, and as they move the illumination changes, giving rise to the variations first noted by American astronomer Edwin P. Hubble. The
nebula was discovered by William Herschel in 1783 (sources: Wikipedia / Spacetelescope.org).
Twenty-two exposures of approximately 3 minutes at ISO 800 with no dark frame subtraction were stacked with Deep Sky Stacker
(resulting in a 1 h 12 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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