M78: This is a reflection nebula in the constellation Orion. The nebula is relatively small compared to the more famous M42 emission nebula in Orion. The blue color is from light emitted by the very young, hot stars being reflected by the surrounding dark gas clouds. Just as it does in our atmosphere, blue light scatters preferentially in these interstellar clouds. Thus the color of this nebula and our sky. For the same reason, many of the stars that are visible through these clouds appear slightly redder than they would up close, because some of their blue light has been scattered away from our direction.
Right Ascension: 5hr 46.7m
Declination: 0° 3'
Apparent Magnitude: 8.3
Date: November 2010
Telescope: Meade 16" Schmidt Cassegrain with f6.3 reducer (used at ~ f6.1)
Camera: SBIG ST-10XE
Luminance Guiding: AO-8
RGB Guiding: PHD, DSI Pro, Meade 5"
Exposure: L: 7x10m, binned 1x1
RGB: 5x5m, binned 2x2
The camera was at -35°
Processing Notes: Data acquisition with CCDSoft. Reduced and aligned in CCDStack and combined with Sigma Combine. Arcsine stretch import of L into Photoshop. Adjusted curves and levels. Increased contrast via a highpass filter overlay layer. Slight blur on the dim areas and sharpening on non-star bright areas. Minimize filter on the stars. Repaired three overexposed stars by overlaying a strong Dust and Scratches filter and only unmasking the areas to be repaired. RGB combined in AstroArt at 1:1:1.6 ratio. Adjusted curves and levels, and reduced noise of RGB. L was combined with RGB using three layers: Luminance on the bottom; RGB as a multiply(35%) layer; and RGB as a color layer on top. Final adjustment and tweak in Photoshop.
Scale: 0.52"/pixel on highest resolution
Links to images of this object on other sites:
Additional Comments: The brightness varies significantly between the bright stars and the dark clouds, making the imaging and processing somewhat of a challenge. There are relatively few stars visible in front of the clouds.
A single 10 minute luminance exposure can be found here:
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