Dual band images - Astrophotography and Spectroscopy

Astro-Imaging and Spectroscopy

Star Party  St Michel  Haute Provence (France)

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Dual band imaging

Dualband imaging with color cameras is a new powerful technique to obtain images of galactic nebulae under light polluted sky.
These filters have two transmission bands in the green/blue region which contain H-beta, OIII and in the red region H-alpha.
A broad dual band filter  is a UHC -Filter ( see Filtertest )
Some Filters also a transmission band for SII.  With the narrow band technique it was necessary to take images with the monochrom camera  throught 2 or 3 filters.
With  the dual band filter and a color  camera it is possible to take  3  lines (H-beta, OIII and H-alpha) in one image. The modern CMOS-Cameras  have a quantum  efficency of  70% -80%.
The combination of these cameras and these dual band filter is a very powerful tool.
Image processing
  • Exposure time more than 2 hours .
  • For CMOS-Cameras - single frame with 4 minutes, with unity gain
  • Data reduction lights, darks, flats and flatdarks are processed with Deepskystacker.
  • Dynamic background extraction with Pixinsight
  • Final tone mapping with Photoshop
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Copyright  Matthias Kiehl

March 2024
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