Rosette Nebula Mosaic in Narrowband Light

The huge Rosette Nebula (NGC2244) is located in the constellation Monoceros, and measures about 90 to 100 light years across (540 trillion to 600 trillion miles). It is estimated to contain hydrogen gas about 10,000 times the mass of our sun, and lies about 5,000 light years away (30 quadrillion miles). In the center of the nebula, young stars are forming from the gas cloud. Intense radiation from these stars excites the gas, causing it to glow brightly.

The Rosette is too large to fit completely on my camera's chip, so I exposed half of it at a time and joined the frames together. The five images below represent 26½ hours total exposure collected over 13 nights in January, February, and March 2008 at various camera temperatures and exposure times.

The images were exposed through filters having extremely narrow bandwidths to capture only the light emitted by certain gasses when excited by stellar radiation. This table lists the exposure for each narrowband channel. For variety, the Rosette is shown using different color palettes to represent three gases present in the nebula. Scroll down to see them all.


Equipment
TMB-130SS APO refractor at f/7 on a Losmandy G-11 equatorial mount
SBIG ST-8XM camera
SBIG CFW-10 filter wheel with Astrodon filters
Guiding: 60mm f/5 refractor and ST-402 camera
Imaging and autoguiding with MaxIm DL 4.57
Exposure
Hydrogen-alpha   9 hours, unbinnned.
Oxygen-III   9 hours unbinnned.
Sulfur-II   8.5 hours unbinnned.
Processing Guiding and exposure using MaxIm DL 4.57
Dark and flat-frame processing in CCDStack
Channel sub-frames statistical-combined in CCDStack
East/west mosaic stitching in MaxIm DL 4.57
Levels, curves and color-combined in Photoshop CS3
Date and Location 13 nights in January, February, & March 2008
Montpelier, VA    N 37° 49' 12", W 77° 42' 06"




Red: Hydrogen-alpha     Green: Synthesized from red/blue     Blue: Oxygen-III + Sulfur-II

The data from the three filters was assigned to this "natural-color" palette in Photoshop. First, the monochrome hydrogen-alpha image was converted to color. Next, the oxygen-III and sulfur-II images were layered one on top of the other, with the blending mode set to "screen" to get data from both images. The two layers were flattened into one, which was copied and pasted into the blue channel of the RGB-mode H-a image, leaving the H-a data in the red and green channels. Finally, the green channel was replaced with data synthesized from the red and blue channels using Noel Carboni's Astronomy Tools for Photoshop.

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(Hubble palette)   Red: Sulfur-II     Green: Hydrogen-alpha     Blue: Oxygen-III

This image uses the same color palette as the Hubble Space telescope. Ionized sulfur is red, hydrogen is green, and oxygen is blue. Click on the image for a larger version.

Along the Rosette's northern arc (top), two cloud tendrils spiral together in a "Y" shape. You can see a closer view of this feature here. Other dark clouds and tendrils can be found in the nebula's western region (right), and here is a closer view of that area. The southeast region (lower-left) contains several pillars of dense gas which is condensing to form new stars. You can see details here.

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Red: Oxygen-III     Green: Sulfur-II     Blue: Hydrogen-alpha

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Red: Sulfur-II     Green: Oxygen-III     Blue: Hydrogen-alpha

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Red: Hydrogen-alpha     Green: Sulfur-II     Blue: Oxygen-III

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Rosette Nebula, Southeastern Region

In the southeast quadrant of the Rosette can be seen several pillars known as "elephant trunks" rising from the surrounding molecular hydrogen gas and dust. The pillars are so dense that gravity contracts the gas to form stars. At the end of the pillars, radiation from the young stars boils away the lower-density material, revealing the stars' gaseous "cocoons." Ultimately the cocoons themselves will boil away, exposing the stars themselves.

This image comprises a total of three hours exposure.


Original version

Equipment Celestron 9¼" at f/5.6 on a Celestron CGE equatorial mount
SBIG ST-8XM camera
Optec IFW filter wheel with Astrodon TruBalance filters
Optec TCF-S focuser
Optec Pyxis camera rotator
Imaging and autoguiding with MaxIm DL 4.11
Exposure
Luminance:   3 hours (12 x 15 min.), unbinned, -20°C
Processing Master dark frame: 32 x 15 min. sigma-reject combined
Dark and flat frame reduction in CCDSoft
Levels and curves, Neat Image, highpass filter in Photoshop CS
Date and Location 27-28 January 2005    Montpelier, VA    N 37° 49' 12", W 77° 42' 06"



Rosette Nebula, Northwest Region

Along the Rosette's northern arc, two cloud tendrils spiral together to make a distinctive "Y" shape. Several small star-forming pillars are found along these clouds, at the bottom of the spiral, and in the dark clouds toward the right (west). Click here for the mosaic including a general view of the northern and western regions.


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Equipment Celestron 9¼" at f/5.6 on CGE equatorial mount
SBIG ST-8XM camera
Optec IFW filter wheel with Astrodon filters
Optec TCF-S focuser
Optec Pyxis camera rotator
Imaging and autoguiding with MaxIm DL 4.11
Exposure
Luminance:   3.3 hours (20 x 10 min.) exposure, unbinned, -30°C
Processing Master dark frame: 4 x 10 min. sigma-reject combined
Dark and flat frame reduction in CCDSoft
Levels and curves, Gaussian blur, highpass filter in Photoshop CS
Date and Location 18 & 26 February 2006    Montpelier, VA    N 37° 49' 12", W 77° 42' 06"



Rosette Nebula, Western Region

This is the western area of the Rosette; north is roughly toward the right. Star-forming pillars are rising from the dark clouds; the three "heads" at the far right are the same ones in the photo above. Click here or here for wider views of this area.


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Equipment Celestron 9¼" at f/5.6 on CGE equatorial mount
SBIG ST-8XM camera
Optec IFW filter wheel with Astrodon filters
Optec TCF-S focuser
Optec Pyxis camera rotator
Imaging and autoguiding with MaxIm DL 4.06
Exposure
Luminance:   Single 30 minute exposure, binned 2x2, -20°C
Processing Master dark frame: 3 x 30 min. average combined
Dark and flat frame reduction in CCDSoft
Levels and curves, Neat Image, highpass filter in Photoshop CS
Date and Location 18 January 2005    Montpelier, VA    N 37° 49' 12", W 77° 42' 06"