by Chris Peterson » Fri Oct 10, 2014 2:14 pm
starsurfer wrote:A HaRGB image would combine the excellent narrowband detail with "true" colour. For example, this HaLRGB image by Bob Franke shows nice detail and the LRGB data helps preserve the many small reflection nebulae in the area:
http://bf-astro.com/ngc6820/ngc6820.htm
I disagree. Still only a fraction of the structure is visible. With HaRGB we still only get a single channel of narrowband, which largely overlaps the dominant wideband signal (most of the light is coming from Ha). It is the addition of the two other narrow channels, combined with the reduction in continuum that lets us see structure.
In addition, our ability to discriminate subtle color changes is very poor in the reds, so we lose additional detail. Simply presenting the Ha data as blue, for instance, would let us see more even in an HaRGB.
We can argue what makes a subjectively more aesthetic image, but there's little doubt that you don't want to include continuum light if the goal is to maximize the information we can take from it.
[quote="starsurfer"]A HaRGB image would combine the excellent narrowband detail with "true" colour. For example, this HaLRGB image by Bob Franke shows nice detail and the LRGB data helps preserve the many small reflection nebulae in the area: [url]http://bf-astro.com/ngc6820/ngc6820.htm[/url][/quote]
I disagree. Still only a fraction of the structure is visible. With HaRGB we still only get a single channel of narrowband, which largely overlaps the dominant wideband signal (most of the light is coming from Ha). It is the addition of the two other narrow channels, combined with the reduction in continuum that lets us see structure.
In addition, our ability to discriminate subtle color changes is very poor in the reds, so we lose additional detail. Simply presenting the Ha data as blue, for instance, would let us see more even in an HaRGB.
We can argue what makes a subjectively more aesthetic image, but there's little doubt that you don't want to include continuum light if the goal is to maximize the information we can take from it.