Separate RGB focus
Posted: Mon Mar 15, 2021 7:31 pm
One idea that might help the focussing of refractors on RGB sensors would be a focus aid like FWHM performed on each colour channel separately, but all displayed together
The focus of each channel is not identical unless one has a very highly corrected telescope, so displaying a focus score for each channel individually may be useful to find the best compromise position.
For example with the Nikon 180mm F2.8 lens, it has been recommended to focus so that some of the stars are slightly pink, as this yields a better overall result
It would also allow the lens/telescope performance to be objectively compared / monitored as other parameters are adjusted, eg aperture stop.
Rather than the processing algoritm working on a 1x1 image with interpolated colour, consider it as 3 (or 4) 2x2 binned monochrome images.
The focus of each channel is not identical unless one has a very highly corrected telescope, so displaying a focus score for each channel individually may be useful to find the best compromise position.
For example with the Nikon 180mm F2.8 lens, it has been recommended to focus so that some of the stars are slightly pink, as this yields a better overall result
It would also allow the lens/telescope performance to be objectively compared / monitored as other parameters are adjusted, eg aperture stop.
Rather than the processing algoritm working on a 1x1 image with interpolated colour, consider it as 3 (or 4) 2x2 binned monochrome images.