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Hubble image colorization



 
 
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  #1  
Old September 9th 03, 03:18 PM
Zbob
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Default Hubble image colorization

I saw a story on the news that there is a "Watergate of space science
going on" in that graphics artists are colorizing the images from
Hubble to make them more pleasing to the public. Can anyone confirm
that story? I would think with spectral data, the colors would be
known and no need to make them up.
  #2  
Old September 18th 03, 04:35 PM
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Default Hubble image colorization

Zbob:

I do NOT work with Hubble images, but rather with images taken of the
surface of the Earth by Earth-orbiting satellites. However, I have
kicked around a lot of digital images, enhancing them so that the subtle
information within the digital data can be made obvious. This is what
is done in "remote sensing."

From my experience, I assume that Hubble images are "enhanced" for the

following reasons:

--1-- in each spectral band, the number of grey levels used by the data
are too few to show details to the rather insensitive human eye. Thus
the data are "stretched" over a larger range of data numbers, e.g., from
an original 35-42 to a resulting 0-128.

--2-- A series of "grey-level" images, each from a "band" in the em
spectrum, are not very informative. Since we humans see color, contrast
enhanced grey-scale data can be projected onto a color monitor (or color
film) with:

--2a-- a different color assignment for each data number. The resulting
color image is a "pseudocolor" image.

--2b-- a different color filter for each selected band. If the red band
is projected through a red filter, green through green, and blue through
blue, then the result is a "natural color" image. If an infrared band
(light which we can not see) is projected through a red filter, red
through a green filter and green through a blue filter, then the result
is a "false color" image.

Different astronomy sensors can look at very different parts of the em
spectrum. Sensors can record such items as the distribution of iron
atoms, hydrogen ions, stellar surface temperatures, etc. Thus, the data
can be shown only when contrast enhanced and colorized. Computers do
not need this, but people do.


Fred

Zbob wrote:

I saw a story on the news that there is a "Watergate of space science
going on" in that graphics artists are colorizing the images from
Hubble to make them more pleasing to the public. Can anyone confirm
that story? I would think with spectral data, the colors would be
known and no need to make them up.


 




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