Re:1800s Astronomical Drawings vs. NASA Images (2016)
by dredmorbius on Wednesday August 18, 2021 @04:58AM
(#28218995)
Most scientific astronomical images are based on capture of specific bandwidths and frequencies, which are then assigned colours for visual interpretation.
Given that many of the frequencies are beyond the limits of human vision (ifra-red, microwave, and radio, at the low end, ultraviolet, x-ray, and gamma-ray at the high), this is somewhat out of necessity.
The individual channels largely record intensity, so in that regard they're similar to B&W photographs, but the intensities are of specific bands, rather than a wide range of bands as in silver-halide based photographs. There may be some frequency variation recorded and interpreted as well, I'm not certain of this.
That said, I'm pretty sure that there's also an eye to aesthetic and public appeal of landmark released images.
This link shows and discusses multi-spectral images, showing the channels individually for several objects:
You can find such examples by searching for different EMR aspects, e.g., "radio, ultraviolet, x-ray". These are typically noted in APOD's image descriptions.
Given that many of the frequencies are beyond the limits of human vision (ifra-red, microwave, and radio, at the low end, ultraviolet, x-ray, and gamma-ray at the high), this is somewhat out of necessity.
The individual channels largely record intensity, so in that regard they're similar to B&W photographs, but the intensities are of specific bands, rather than a wide range of bands as in silver-halide based photographs. There may be some frequency variation recorded and interpreted as well, I'm not certain of this.
That said, I'm pretty sure that there's also an eye to aesthetic and public appeal of landmark released images.
This link shows and discusses multi-spectral images, showing the channels individually for several objects:
https://ecuip.lib.uchicago.edu/multiwavelength-astronomy/ast...
The Crab Nebula at frequncies from radio to gamma: https://upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Cr...
Galaxy Centaurus-A image which includes infrared and x-ray channels: https://apod.nasa.gov/apod/ap210117.html
Today's APOD shows the Ring Nebula in infrared, red, and visible light: https://apod.nasa.gov/apod/ap210818.html
You can find such examples by searching for different EMR aspects, e.g., "radio, ultraviolet, x-ray". These are typically noted in APOD's image descriptions.