Mustapha Mond wrote: chikie wrote: ukimalefu wrote:
Mustapha Mond wrote: How much false color goes into space photos these days?
"false color" doesn't mean that they use whatever color to make it look pretty, it means that the color is not on the original picture. The basic color comes from red-green-blue filters, and I believe that by analyzing all the data of any given space object they can estimate what color something should be, so I believe this "false color" images are very close to the real color, because science.
False color has nothing to do with what color something should be and everything to do with different levels of reflectivity / emissivity of the surface at different EM wavelengths. Many picture making sensors at least straddle the visible and near-infrared bands, while lots also look at stuff like X-rays, ultraviolet, and thermal-infrared bands.
It has nothing to do with how the object "looks" and everything to do with the physical properties of the object's surface. Only when you're looking at a true color image do the colors correspond with real colors. Assigning different bands to different colors emphasizes different characteristics that help scientists with their analyses.
This is why lots of satellite photos of earth have vegetation in red. Chlorophyl is very reflective in the near-IR (that is, in the infrared spectrum but close to the visible). Assigning that band from the satellite as "red" makes vegetation very visible if you're trying to do some sort of vegetation analysis.
Whatever the technical reason, my understanding is that most of outer space looks pretty boring to the naked eye, as much as we want it to look like science fiction.
The simple fact is even when limited to the visual range that astrophotography is doing two things that human eyes cannot:
1) in effect opening an eye's pupil to the size of whichever instrument is being used, so a fully dark-adapted iris being about 7 mm in diameter would be, in effect, enlarged to up to 10.4 meters for the currently largest telescope, and
2) storing the gathered light for as long as days at a time when the eye's retina refreshes its imaging in terms of milliseconds.
The fact that one can see color at all when one looks at Jupiter through a 40mm set of binoculars is due to the first difference above ([40mm/7mm]^2≈33 times the light-gathering of the human eye alone). If and when humans bodily get to Jupiter, the planet will be a dull grey with some hints of color.
I got to see the Orion Nebula through a 17-inch (432 mm) telescope. Even with just over 3800 times the light-gathering that that light-bucket gave me I got to see a bright green object.