The northern part of NGC6992 imaged with the 43cm f6,8 PlaneWave CDK17 and a FLI Kepler 4040 CMOS camera.
It's a special tri-color narrowband image.
Special with regards to the used filters.
Most common is the SHO palette in, this case the following filters have been used, H-alpha, Nitrogen and Oxygen.
The nitrogen emission line is very close to the h-alpha with regards to the wavelengh.
Only by using filters with a bandwith of 3nm or less the two emission lines can be seperated.
So that a tri color image can be made with a nitrogen filter instead of an sulfur filter.
I have done the HNO palette.
Integration time HNO = 177:360:297 minutes