Butterfly and Crescent Nebulae in constellation Cygnus
Image is in mapped colors, from the emission of ionized elements, R=Sulfur, G=Hydrogen and B=Oxygen.
The colorful "noise" at background is not a noise but countless number of stars!
This is a part of the much large, 18-panels, mosaic of constellation Cygnus, it can be seen HERE.
Image is shot at Autumn 2011, I'm publishing this here, since I have reprocessed the color data.
Image is shot with Canon EF 200mm f1.8 optics, full open, QHY9 cooled astronomical camera and the Baader narrowband filter set. (H-a. O-III and S-II) Esposure times, about two hours per channel, total six hours.
Shooting with f1.8 optics is kind of extreme, the critical focus zone is only 7 microns (7/1000mm).
Focusing and staying in focus is really difficult at that speed, one quarter of the degrees temperature drop is enough to destroy focus. I have build a temperature compensating automatic focusing system for camera lenses. ( http://astroanarchy.blogspot.fi/2008/09/new-equipmets-and-some-development-work.html )
A closeup image of the Crescent Nebula,
it can be seen at center of the image above
Image is in HST-palette, (HST=Hubble Space Telescope)
from the emission of ionized elements, R=Sulfur, G=Hydrogen and B=Oxygen.
Star colors are mixed from the NB channels, Red=H-a, G=O-III and B= 85%O-III + 15%H-a.
This image was selected as an APOD, Astronomy Image Of the Day, by the NASA.
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