Note, however, that this spectrum is completely useless for understanding the color of the Owl Nebula. M57 has less reflected light compared with emitted light (although you can still see some continuum light). A spectrum of the Owl Nebula would not look like a flat zero line with spikes at the emission sources, but like a low hot blackbody curve with spikes sitting on top of it. You're going to have a very difficult time assessing the color that someone would perceive when you look at a spectrum like that.Ann wrote:Yes, but now look at the two spectra you posted in a previous post.
That said, consider the M57 spectrum. The 501 nm line will not appear as green or blue at all, because that line is not in isolation. We can simplify the spectral output to a 501 nm line and a 656 nm line. Visually, individually, these would appear as cyan and red. Present these two lines to the human eye, however, and we'll perceive yellow. In reality, we see something pushed down towards green because our eyes are more sensitive to the shorter wavelength line. The important point, however, is that we'll see a color substantially different than what we'd see with just the 501 nm line in isolation.