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Emission nebulae

Emission nebulae contain gasses that absorb light from the stars and emit the absorbed energy at distinct wavelengths (colors). The emitted wavelengths correspond exactly to the electron energy levels of the gas atoms. Important emission lines in the visible spectrum are :

    - Hydrogen-alpha (Ha) at 656 nm
    - Double ionized oxygen (Oiii) at 501 nm
    - Single ionized sulfur (Sii) at 672 nm

The pictures below were taken with narrowband filters that pass through only one of these wavelengths each. Color images are generated by letting the three emission lines represent one "primary color" each. It is common to choose primary colors that are separated by 120º on the color wheel.

For example: 	R = red  	G = green  	B = blue  
or 		C = cyan  	M = magenta  	Y = yellow   

 

NGC2070 "Tarantulla" nebula with Ha-Oiii-Sii filters

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NGC2070 photographed from the remotely operated GRAS observatory in Australia 14.08.2006.
Telescope A6: Intes 150mm with SBIG ST-10. FOV: 56'x38'. RGB=Ha:Oiii:Sii (3x3:3x3:3x3 min).
Processed with MaximDL, Photoshop and NeatImage: calibrated, stacked,
combined rgb, noise reduction, contrast adjustments. Full size version.

Part of IC1318 "Butterfly" nebula with Ha filter

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Part of IC1318 photographed from the remotely operated GRAS observatory in New Mexico, 27.08.2006.
Telescope A5: Takahashi 250mm with SBIG ST-8. FOV: 55'x37'. Ha (5x5 min). Processed with MaximDL, Photoshop
and NeatImage: calibrated, stacked, noise reduction, contrast adjustments. See Full size version.

"Elephant trunk" nebula near vdB142 with Ha filter

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Elephant trunk (bottom right area of the IC1396 image below) photographed from the remotely operated GRAS observatory in New Mexico 27.08.2006. Telescope A5: Takahashi 250mm with SBIG ST-8. FOV: 50'x24'. Ha (4x5 min). Processed in
MaximDL, Photoshop and NeatImage: calibrated, stacked, noise reduction, contrast adjustments. See full size.

IC1396 with Ha-Oiii-Sii-filter

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IC1396 photographed from the remotely operated GRAS observatory in New Mexico 28.05.2006.
Telescope A3: Takahashi 90mm with SBIG ST-110XE. FOV: 123'x84'. RGB=Ha:Oiii:Sii (3x7:3x7:3x7 min).
Processed with MaximDL and Photoshop: debloomed, calibrated, stacked, combined rgb,
color saturation, contrast adjustments. See larger version, full size.

M16 "Eagle" nebula with Ha-Sii-Oiii filters

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M16 through the remotely operated RaS telescope "Areo2" in New Mexico, 05.06.2006.
Telescope A2: Takahashi 300mm with SBIG ST-8. FOV: 13.2'x8.8'. LRGB=Ha:Ha:Sii:Oiii (4x4:1x4:1x4 min).
Processed with MaximDL, Photoshop and NeatImage: calibrated, stacked, noise reduction,
contrast adjustments. See larger version , full size , Ha only.

NGC6992 "Veil nebula" with Ha-Oiii-Sii filters

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NGC6992 through the remotely operated RaS telescope "Areo3" in New Mexico, 06.06.2006.
Telescope A3: Takahashi 90mm with SBIG ST-10. FOV: 119'x78'. YCM=Ha:Oiii:Sii, (4x5:4x5:4x5 min).
Processed in MaximDL and Photoshop: calibrated, stacked, combined rgb, contrast adjustments.
See larger version, full size. Click here to see other versions (brighter, RGB encoding, etc.)

M42 "trapeze" area with narrowband filters

Click to see larger version   Click to see larger version
The trapeze area in M42 photographed with my Art285 camera through C11 i prime focus at the
TAF observatory in Trondheim. Filters and exposures: RGB = Ha-Oiii-Sii (18x2:16x2:13x3.5 sec),
2x2 binning. No guiding. Different contrast adjustments for the two versions.

The picture above was my first successfull deep-sky exposure with Artemis-285. It was taken at the observatorium of the local astronomy society near Trondheim, Norway, on the 8. of December 2005 with good help from Birger Andresen and Erlend Langsrud.

Processing:
      - Darkframe correktion and stacking in K3CCDtools
      - Combined color channels: R=Ha, G=Oiii, B=Sii
      - Some offset subtracted from the Ha-kanalen.
      - Unsharp mask (Matlab routine)
      - Adjustment of the contrast curve to enhance dark areas.

 

Erlend Rønnekleiv, www.eronn.net
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