N.Am. Nebula (Yucatan)
S[II]:H-alpha:O[III]

N.Am. Nebula (Yucatan)
S[II]:H-alpha:O[III]:
The North America Nebula is in the constellation Cygnus, about 3° from the star Deneb. The entire nebula has an area of more then four times the size of the full moon, but the field of view of this image is just a fraction of the nebula - an area of less then half a full moon, centered near the "Yucatan" part of North America, including the end of the "Cygnus Wall" star forming region. North is to the right in this image. This composite narrow band image is the result of three images taken with filters showing the presence of singly ionized sulfur (S[II]) assigned to red, atomic hydrogen (H-alpha) assigned to green, and doubly ionized oxygen (O[III]) assigned to blue. This choice of color assignment is often called the Hubble palette, because this was the choice of colors used in the early Hubble photo of the Eagle nebula. The data here include over 8 hours of exposure time.

The pink stars are a processing artifact. In "natural" light, the H shows up as red. Here H is assigned to green. Since almost everything is H, if equal parts were used, the entire picture would be green and the stars white. To make the S and O in the clouds be comparable in brightness for this three color image, those channels needed to be "stretched", or enhanced so that they show up at all. However, that makes the stars that much brighter in the red and blue channels. The ratios to make the color in the clouds appealing leaves the stars mostly pink. Notice that the stars in the Hubble image of the Eagle nebula (Pillars of Creation) are also pink. http://apod.nasa.gov/apod/ap070218.html

NGC: 7000
Right Ascension: 20h 57m 38s
Declination: 43d 26m 41s
Apparent Magnitude: 4, for the entire nebula

Date: June 2014
Equipment:
Telescope: Meade 16" Schmidt Cassegrain with f6.3 reducer
Camera: SBIG ST-10XE
Guiding: Meade 5" refractor; Starshoot Autoguider; PHD

Exposure:
20x10 min S[II], binned 2x2 (red)
14x10 min H-alpha, binned 2x2 (green)
16x10 min O[III], binned 2x2 (blue)
Processing Notes: Data acquisition with CCDSoft. Reduction, and alignment in CCDStack. Data selection and combination with Sigma Combine. Slight smoothing in dimmer areas. Stars were slightly elongated (from autoguiding issues) and were repaired in Photoshop. Overall sharpening was via unsharp mask. Individual color components were combined and aligned in Photoshop. Curves applied for final color balance. Slight increase in contrast was by a high-pass filter of a desaturated layer applied as an overlay.
Scale: 1.06"/pixel

Links to images of this object on other sites:
http://apod.nasa.gov/apod/ap000501.html
http://www.qdigital-astro.com/astrogallery/ngc7000-north-american-nebula-and-the-cygnus-wall-in-tric

Additional Comments: Data acquisition and processing of this image was a collaborative effort between summer Space Grant students Gayle Owen, Theo Wecker, Kevin Graves, and Geoff Johnson. This version of the color stack was assembled by Charles Hakes. We could still take more H-alpha frames after some guiding issues have been resolved. The stars could use additional "rounding and minimizing" in the individual frames - especially the S[II] and the O[III]. We also plan to acquire luminance data to increase the overall resolution, and possibly will acquire RGB data to add star colors to the image.

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