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M33 is one of the galaxies in our Local Group (galaxies near our own). It is estimated to contain only about 20 billion stars, compared to M31's 300 billion. M33 is about the same distance away as M31, or possibly slightly closer.
Technical. Canon 7D 18-megapixel digital camera, Canon 300 mm f/2.8 II lens at f/2.8. 35 one-minute exposures at ISO 1600 were added (35 minutes total exposure). No dark frame subtraction, no flat fields, no noise reduction. Tracking with an astrotrac. Slight crop.
The Exposure Factors, CEF, CEFA are measures of the relative amounts of light received from a subject. It can be used to fairly compare wildly different lens/telescope apertures and exposure times. For this image:
Modern DSLRs like the 7D include on sensor dark current suppression and low fixed pattern noise at ISOs around 1600 and higher, making no need for dark frame subtraction. Modern raw converters correct for light fall-off and also correct for hot/dead/stuck pixels. This makes processing low light images easy: simply align and average.
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Keywords to this image = astrophoto-1 galaxy Messier night low-light digital_astro
Image ID: m33_300mm.35min.c09.26.2014.IMG_2360-400.f-bin2x2s.jpg
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Last updated May 26, 2023