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
