by Chris Peterson » Fri Feb 19, 2016 3:03 pm
Guest wrote:I understand where the 'spikes' around the stars come from, but I am wondering about the 'halo' or glow around them too. Is the halo the result of a) interstellar dust scattering of light (a dirty galaxy); b) scattering of light by dust in our solar system (a dirty solar system); c) scattering caused by the optics (lenses) of the viewing instrument (dirty lenses or glass impurities); or d) saturation of the optical chip around the single point sources? Or some combination of the above. And if a combination, what proportions could be attributed to each? Ideas or opinions?
From (a), none. From (b), none. From (c), some. And also from seeing effects- the wiggling of the stellar position caused by our moving atmosphere. You're on the right track with (d), but it isn't saturation. The fact that we are seeing the color of the stars even at their cores demonstrates that the data isn't saturated. But the stars are, in fact, much brighter than the galaxy. And the brighter a star, the larger its physical diameter, since we can see further out along the wings of its diffracted image.
This image was made with a high end scope, but it still has two mirrors that have somewhat rough surfaces. So what we're seeing is combination of the above mentioned diffraction, scatter off the mirrors, and internal reflections in the filters and CCD detector.
[quote="Guest"]I understand where the 'spikes' around the stars come from, but I am wondering about the 'halo' or glow around them too. Is the halo the result of a) interstellar dust scattering of light (a dirty galaxy); b) scattering of light by dust in our solar system (a dirty solar system); c) scattering caused by the optics (lenses) of the viewing instrument (dirty lenses or glass impurities); or d) saturation of the optical chip around the single point sources? Or some combination of the above. And if a combination, what proportions could be attributed to each? Ideas or opinions?[/quote]
From (a), none. From (b), none. From (c), some. And also from seeing effects- the wiggling of the stellar position caused by our moving atmosphere. You're on the right track with (d), but it isn't saturation. The fact that we are seeing the color of the stars even at their cores demonstrates that the data isn't saturated. But the stars are, in fact, much brighter than the galaxy. And the brighter a star, the larger its physical diameter, since we can see further out along the wings of its diffracted image.
This image was made with a high end scope, but it still has two mirrors that have somewhat rough surfaces. So what we're seeing is combination of the above mentioned diffraction, scatter off the mirrors, and internal reflections in the filters and CCD detector.