by Ann » Fri Dec 30, 2016 2:36 pm
DavidLeodis wrote:As various color palettes are used to produce astronomy images I will be grateful if someone could please state what colors are likely represented by each of the ionized sulfur, hydrogen and oxygen in the false color image. The explanation states the clouds are "dominated by emission from hydrogen" which might therefore be the brownish orange areas as they cover more than the bluish and other areas. Thanks in advance for any help.
Well, hmmm. I apologize for answering this question as a person who doesn't much like the Hubble palette.
Basically, when we talk about "three-filter-images" shown in false or mapped color, the shortest wavelength filter image is mapped as blue, the middle wavelength filter image is mapped as green, and the longest wavelength filter image is mapped as red.
The wavelength of OIII is 500.7 nm. Hα is 656.28 nm. SII is 671.83 nm (I think). Very occasionally, I think NII is being used instead of SII, and its wavelength is 658.35 nm. In any case, you can see that the wavelengths of SII and NII (particularly NII) are very similar to Hα, but Hα is still a little shorter than either of them.
Therefore, OIII, the shortest wavelength, is mapped as blue, Hα, the middle wavelength, is mapped as green, and SII (or even NII), the longest wavelength, is mapped as red.
The Pleiades in three infrared wavelengths, 4.5 µm (mapped as blue),
8.0 µm (mapped as green) and 24.0 µm (mapped as red).
John Stauffer (Spitzer Science Center, Caltech)
NASA/JPL-Caltech/J. Stauffer (SSC/Caltech)
The same principle is used for three-filter infrared images: the shortest infrared wavelength is mapped as blue, the middle one as green and the longest one as red.
Ann
[quote="DavidLeodis"]As various color palettes are used to produce astronomy images I will be grateful if someone could please state what colors are likely represented by each of the ionized sulfur, hydrogen and oxygen in the false color image. The explanation states the clouds are "dominated by emission from hydrogen" which might therefore be the brownish orange areas as they cover more than the bluish and other areas. Thanks in advance for any help.[/quote]
Well, hmmm. I apologize for answering this question as a person who doesn't much like the Hubble palette.
Basically, when we talk about "three-filter-images" shown in false or mapped color, the shortest wavelength filter image is mapped as blue, the middle wavelength filter image is mapped as green, and the longest wavelength filter image is mapped as red.
The wavelength of OIII is 500.7 nm. Hα is 656.28 nm. SII is 671.83 nm (I think). Very occasionally, I think NII is being used instead of SII, and its wavelength is 658.35 nm. In any case, you can see that the wavelengths of SII and NII (particularly NII) are very similar to Hα, but Hα is still a little shorter than either of them.
Therefore, OIII, the shortest wavelength, is mapped as blue, Hα, the middle wavelength, is mapped as green, and SII (or even NII), the longest wavelength, is mapped as red.
[float=left][img2]https://apod.nasa.gov/apod/image/0704/m45_spitzerR720.jpg[/img2][c][size=85]The Pleiades in three infrared wavelengths, 4.5 µm (mapped as blue),
8.0 µm (mapped as green) and 24.0 µm (mapped as red).
John Stauffer (Spitzer Science Center, Caltech)
NASA/JPL-Caltech/J. Stauffer (SSC/Caltech)[/size][/c][/float]The same principle is used for three-filter infrared images: the shortest infrared wavelength is mapped as blue, the middle one as green and the longest one as red.
Ann