by spinlock » Wed Feb 19, 2020 4:57 pm
Ann wrote: ↑Wed Feb 19, 2020 7:29 am
It is interesting to compare today's APOD with the original image of this galaxy, published on
Space Telescope's own website.
As you can see, the color balance of the APOD is much bluer, so blue that the lenticular, "red and dead" barred galaxy at upper right looks blue, even though it totally lacks any sign of star formation. The likely reason for the blue color balance of the APOD is that the original image is a two-filter image, where the filters are 606 nm (centered on orange) and 814 nm (near infrared). Presumably the 606 nm filter image has been treated as blue in the APOD, or at least a bright shade of cyan. In my opinion, there is very little "true cyan" in UGC 12591 or in any of its neighboring galaxies, which is to say that the original Space Telescope image looks much more "natural" to me.
The details in the dust lane of UGC 12591 have also been sharpened in the APOD.
...
Ann
I acknowledge the sin of having too much of the blue color in galaxies halos, as I also thought it could be wrong in attempt to simulate "natural colors" from bi-color data. I was trying to make a clearer view of faint galaxies in the background as well as making the dust lanes more visible, while reducing the green cast of the
original image. It's interesting to know that raw linear image has quite bright halo at the center of UGC 12591, which essentially hides all details of the core and some of the the galaxy's ring structure at its distant side. The APOD image brings out these details at the expense of making that central halo much dimmer.
BTW, I couldn't find catalog name of the galaxy at upper right corner, and therefore no description of it.
Leo Shatz
[quote=Ann post_id=299700 time=1582097370 user_id=129702]
[float=left][img3="UGC 12591: The Fastest Rotating Galaxy Known
Image Credit: NASA, ESA, Hubble; Processing & Copyright: Leo Shatz"]https://apod.nasa.gov/apod/image/2002/UGC12951_HubbleShatz_960.jpg[/img3][/float] [float=right][img3="UGC 12591. Image from https://www.spacetelescope.org/images/potw1709a/."]https://cdn.spacetelescope.org/archives/images/screen/potw1709a.jpg[/img3][/float]
It is interesting to compare today's APOD with the original image of this galaxy, published on [url=https://www.spacetelescope.org/images/potw1709a/]Space Telescope's own website[/url].
As you can see, the color balance of the APOD is much bluer, so blue that the lenticular, "red and dead" barred galaxy at upper right looks blue, even though it totally lacks any sign of star formation. The likely reason for the blue color balance of the APOD is that the original image is a two-filter image, where the filters are 606 nm (centered on orange) and 814 nm (near infrared). Presumably the 606 nm filter image has been treated as blue in the APOD, or at least a bright shade of cyan. In my opinion, there is very little "true cyan" in UGC 12591 or in any of its neighboring galaxies, which is to say that the original Space Telescope image looks much more "natural" to me.
The details in the dust lane of UGC 12591 have also been sharpened in the APOD.
...
Ann
[/quote]
I acknowledge the sin of having too much of the blue color in galaxies halos, as I also thought it could be wrong in attempt to simulate "natural colors" from bi-color data. I was trying to make a clearer view of faint galaxies in the background as well as making the dust lanes more visible, while reducing the green cast of the [url=https://www.spacetelescope.org/images/potw1709a/]original image[/url]. It's interesting to know that raw linear image has quite bright halo at the center of UGC 12591, which essentially hides all details of the core and some of the the galaxy's ring structure at its distant side. The APOD image brings out these details at the expense of making that central halo much dimmer.
BTW, I couldn't find catalog name of the galaxy at upper right corner, and therefore no description of it.
Leo Shatz