by NoelC » Wed May 07, 2008 5:22 pm
My first thought was that it wasn't a particularly accurate composite, insofar as the moon's silhouette shouldn't be that much darker than the surrounding sky, but it did illustrate the phenomenon nicely.
Oh, and everyone should know that there's a substantial amount of digital processing in virtually every astroimage you see. There is the requirement, for example, to overcome limitations of the equipment (e.g. image noise) by averaging multiple exposures. And let's not forget that most astro images are attempting to illustrate objects with dynamic ranges FAR exceeding the equipment's capabilities. Even the light reflected by the atmosphere has to be removed to truly see what's out there.
Personally, I'm most fond of astroimages that represent the colors of objects much as we would see them if we COULD see them with our eyes - for example, glowing red hydrogen, orange and blue stars, brownish dust obscuring the Milky Way, bluish reflection nebulae, etc. False color imagery is fine as long as it's identified as such. How many folks have been confused by the oddball colors in Hubble images, for example? The instrument is a science tool, and as such very few images have actually been made with wideband visual red, green, and blue filters. So people assemble what is captured by the scientists and assign arbitrary colors.
One thing I've always dreamed of doing is to look through an eyepiece of a truly huge telescope, and actually see the colors of what's out there. Of course, star colors we can see visually from home, but the colors of nebulae and galaxies... No way.
-Noel
My first thought was that it wasn't a particularly accurate composite, insofar as the moon's silhouette shouldn't be that much darker than the surrounding sky, but it did illustrate the phenomenon nicely.
Oh, and everyone should know that there's a substantial amount of digital processing in virtually every astroimage you see. There is the requirement, for example, to overcome limitations of the equipment (e.g. image noise) by averaging multiple exposures. And let's not forget that most astro images are attempting to illustrate objects with dynamic ranges FAR exceeding the equipment's capabilities. Even the light reflected by the atmosphere has to be removed to truly see what's out there.
Personally, I'm most fond of astroimages that represent the colors of objects much as we would see them if we COULD see them with our eyes - for example, glowing red hydrogen, orange and blue stars, brownish dust obscuring the Milky Way, bluish reflection nebulae, etc. False color imagery is fine as long as it's identified as such. How many folks have been confused by the oddball colors in Hubble images, for example? The instrument is a science tool, and as such very few images have actually been made with wideband visual red, green, and blue filters. So people assemble what is captured by the scientists and assign arbitrary colors.
One thing I've always dreamed of doing is to look through an eyepiece of a truly huge telescope, and actually see the colors of what's out there. Of course, star colors we can see visually from home, but the colors of nebulae and galaxies... No way.
-Noel