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NGC 7635 (Bubble Nebula)
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| Mouse-over to see annotations. (Requires Javascript) Click to see high-res version. |
Image Details:
- Camera: SBIG ST-2000XM
- Mount: Astro-Physics 1200GTO
- Scope: AP Starfire 160EDF APO Refractor
- Configuration: Prime Focus
- Additional Optics: n/a (Prime)
- Filter: Astrodon SII, Hα, OIII 6nm Filters
- Effective Focal Length: 1200mm
- Effective Focal Ratio: f/7.5
- Exposure: {8 Hα, 14 OIII, 16 SII} × 32min @ -15°C
- Total Exposure: 20hrs, 16min
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- Date: 8/9/2008
- Location: Saratoga, CA, USA
- Acquisition: CCD Commander
- Focus: FocusMax
- Dithering: CCD Commander
- Guiding: Self Guided
Processing:
- IRIS: Registration
- JimP: Dark subtraction, Flat field, Kappa-Sigma Stacking, White balance, ASINH stretching
- Photoshop: JPG conversion
- CCDStack: Deconvolution
Image Description:
This is NGC 7635, aka, the “Bubble Nebula”, an emission nebula in the constellation of Cassiopeiae. This is the first tricolor narrowband image with my new AP 160 Starfire EDF refractor.
Mousing off the image reveals a “Hubble Palette” narrowband image, with
R:G:B = SII:Hα:OIII . Mouse-over the image to see a pseudo-“True Color” image, in which those narrowband emission lines are mapped to their approximate color as seen by human vision. Specifically, the red SII and Hα wavelengths are mapped to red, and the aqua (blue-green) OIII wavelength is mapped to both green and blue. Also, a smidge of Hα is added into blue to simulate the Hβ wavelength.Even after 8 hours of Sii data and 7 hours of Oiii, the image was still fairly noisy in those channels, so I replaced the luminance with the Hα image and cranked the color saturation a little. This really tamed the noise while preserving the essence of the tricolor image.
A higher resolution image is also available. North is up.