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The region around the North America nebula, NGC 7000, and the Pelican nebula to the right of NGC 7000. The colors in the scene illustrate the composition: black is thick dust, orange is dust absorbing distant star light, and reds, pink, magentas is from hydrogen emission nebulae. The small amount of blue in the North America nebula is from the blue emission of hydrogen-beta. Where the nebula is redder, the blue H-beta is being absorbed by dust.
Technical. This image was obtained with a standard Canon 7D Mark II 20-megapixel digital camera and a Canon 200 mm f/2.8 L lens at f/2.8 and ISO 1600. No dark frame subtraction, no flat fields. Tracking with an Astrotrac and no guiding. The total exposure was 52 minutes: 52 one-minute exposures. This is a crop from the full image and presented at 1/3 of full resolution.
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:
This image was made with the first quarter Moon high in the sky, which added a lot of light to the night sky brightness. But that added light was subtracted in post processing revealing the faint nebulae in the area.
Modern DSLRs like the 7D Mark II 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.
To learn how to obtain stunning images like this, please visit my Extensive Articles on Photography .
See my review of the Canon 7D Mark II and why it is so good for astrophotography: Canon 7D Mark II sensor analysis.
Keywords to this image = astrophoto-1 nebula night low-light digital_astro canon_7d2
Image ID: north-america-nebula.c07.25.2015.0J6A4162-213-c-c1-1181s.jpg
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Last updated July 31, 2020