by Ann » Thu Sep 09, 2021 7:17 am
Guest wrote: ↑Thu Sep 09, 2021 5:54 am"M16 Cose Up" ??
Cose up? No. Close up? Sure!
M16 (arrow) widefield. Credit: eBear Foto.
In the picture at right, you can see what M16 looks like when it is not close up. Note that in any sort of RGB photography, M16 will not look blue like it does in the APOD. The blue color
█ in the APOD represents doubly ionized oxygen, OIII, whose wavelength is 501 nm, making its true color look like this:
█. Green color
█ in the APOD represents Hα, hydrogen alpha, whose wavelength is 656nm, which makes it all red:
█. Red in the APOD either represents ionized sulfur, SII, which at 673 nm is also all red
█, or ionized nitrogen, which at 658 nm is also all red
█.
In RGB photography, like in the picture at right, a nebula like M16 will look reddish-pink. Red Hα completely dominates the light of the nebula, but the color is diluted by Hβ, hydrogen beta, at 486 nm, whose color is bluish cyan:
█. OIII
█ also dilutes the color of the nebula close to the hottest stars.
The ESO image above gives you a good idea of what the Eagle Nebula would look like to our eyes, if our eyes were many times more sensitive to faint colored light than they are. The bluish hue in parts of the nebula is due partly to the emission of OIII, but more to the fact that light from many hot blue stars is being scattered in the nebula.
Ann
[quote=Guest post_id=316512 time=1631166874]"M16 Cose Up" ??[/quote]
Cose up? No. Close up? Sure!
[float=left][img3="M16 Close Up. Image Credit & Copyright: Martin Pugh"]https://apod.nasa.gov/apod/image/2109/M16SHO_1024.jpg[/img3][/float][float=right][attachment=0]M16 with arrow and M17 eBear Foto.png[/attachment][c][size=85][color=#0040FF]M16 (arrow) widefield. Credit: eBear Foto.[/color][/size][/c][/float]
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In the picture at right, you can see what M16 looks like when it is not close up. Note that in any sort of RGB photography, M16 will not look blue like it does in the APOD. The blue color [color=#0040FF]█[/color] in the APOD represents doubly ionized oxygen, OIII, whose wavelength is 501 nm, making its true color look like this: [color=#00ff92]█[/color]. Green color [color=#008000]█[/color] in the APOD represents Hα, hydrogen alpha, whose wavelength is 656nm, which makes it all red: [color=#FF0000]█[/color]. Red in the APOD either represents ionized sulfur, SII, which at 673 nm is also all red [color=#FF0000]█[/color], or ionized nitrogen, which at 658 nm is also all red [color=#FF0000]█[/color].
In RGB photography, like in the picture at right, a nebula like M16 will look reddish-pink. Red Hα completely dominates the light of the nebula, but the color is diluted by Hβ, hydrogen beta, at 486 nm, whose color is bluish cyan: [color=#00efff]█[/color]. OIII [color=#00ff92]█[/color] also dilutes the color of the nebula close to the hottest stars.
[float=left][img3="M16 in RGB (or close to RGB). Credit: ESO." ]https://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Eagle_Nebula_from_ESO.jpg/1024px-Eagle_Nebula_from_ESO.jpg[/img3][/float]
[clear][/clear]
The ESO image above gives you a good idea of what the Eagle Nebula would look like to our eyes, if our eyes were many times more sensitive to faint colored light than they are. The bluish hue in parts of the nebula is due partly to the emission of OIII, but more to the fact that light from many hot blue stars is being scattered in the nebula.
Ann