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You all have seen the Hubble's breathtaking space panoramas. They aren't just simple photographs, but digital composites made of two or more greyscale images taken by different cameras onboard the space telescope. This video reveals exactly how they do it.

This time lapse shows how the image of NGC 3982—a spiral galaxy 68 million light-years from Earth, in the Ursa Major constellation—was made using seven grayscale images captured using three of Hubble cameras. The processing job took 10 hours of scaling, rotating, aligning, color processing and missing pixels and artifacts restoration. This doesn't have anything to do with how Photoshop processes RAW files: The "raw" data in these layer composites is all grayscale and registers invisible light as well as visible light. As the video shows, the final image color is fake and assigned by the scientists to display selected features, as they see fit.

But the Photoshop compositing doesn't mean that the images are false—even while at times they appear to be total fantasy. And it doesn't mean that, if we went there in a spaceship, all of Hubble's images would be different from what we could see in person.

The Photoshop processing just transforms the raw data into a format that humans can see. Our eyes are only capable of registering a very limited part of the electromagnetic spectrum, from 390 to 750 nm, while Hubble can see the optical, ultraviolet, and near-infrared spectrums. That's a lot more detail than what we can see with our bare eyes.

This Video Reveals How NASA Photoshops Hubble's Images



Scientists have to choose how to represent this information in a way that we can observe directly. Sometimes they will use a natural representation, which is very close to what we would see if we zoomed there inside the Enterprise. Other times they will choose representative color, which helps them see invisible features of the object—like those that can only be captured in infrared or ultraviolet light. And sometimes they show the image in enhanced color, a hyperrealist mode that brings a lot of hidden, subtle details.

Personally, I don't care how they do it. They will keep amazing me every time I look at them. [HubbleSite]

Color as a Tool
http://hubblesite.org/gallery/behind_th ... _of_color/

Taking color pictures with the Hubble Space Telescope is much more complex than taking color pictures with a traditional camera. For one thing, Hubble doesn't use color film — in fact, it doesn't use film at all. Rather, its cameras record light from the universe with special electronic detectors. These detectors produce images of the cosmos not in color, but in shades of black and white.
Finished color images are actually combinations of two or more black-and-white exposures to which color has been added during image processing.
The colors in Hubble images, which are assigned for various reasons, aren't always what we'd see if we were able to visit the imaged objects in a spacecraft. We often use color as a tool, whether it is to enhance an object's detail or to visualize what ordinarily could never be seen by the human eye.

Light and Filters
http://hubblesite.org/gallery/behind_th ... ilters.php

Light from astronomical objects comes in a wide range of colors, each corresponding to a particular kind of electromagnetic wave. Hubble can detect all the visible wavelengths of light plus many more that are invisible to human eyes, such as ultraviolet and infrared light.
Astronomical objects often look different in these different wavelengths of light. To record what an object looks like at a certain wavelength, Hubble uses special filters that allow only a certain range of light wavelengths through. Once the unwanted light has been filtered out, the remaining light is recorded.

How Filters Work
http://hubblesite.org/gallery/behind_th ... hubble.php

Hubble's many filters allow it to record images in a variety of wavelengths of light. Since the cameras can detect light outside the visible light spectrum, the use of filters allows scientists to study "invisible" features of objects — those only visible in ultraviolet and infrared wavelengths.
In the example to the left, galaxy NGC 1512 is represented in several different wavelengths. Hubble isolates these specific wavelengths using special filters. Choosing a particular filter reveals an image of the galaxy taken through that filter — that is, in a specific wavelength range. The finished image at the far left is actually a combination of all the filtered images.

Red + Green + Blue
http://hubblesite.org/gallery/behind_th ... or/rgb.php

Many full-color Hubble images are combinations of three separate exposures — one each taken in red, green, and blue light. When mixed together, these three colors of light can simulate almost any color of light that is visible to human eyes. That’s how televisions, computer monitors, and video cameras recreate colors.

Hubbles Color Toolbox
http://hubblesite.org/gallery/behind_th ... oolbox.php

See some of the ways we use color by exploring a few of Hubble's most famous images.
Click on one or more of the images at left to explore their color secrets.

Example:

Enhanced Color:
http://hubblesite.org/gallery/behind_th ... atseye.php

Cat's Eye Nebula
The Cat’s Eye Nebula consists of glowing gases ejected into outer space by a dying star. Individual chemical elements in the nebula emit light at very specific wavelengths.
The three black-and-white images used to construct this image represent light from hydrogen atoms, oxygen atoms, and nitrogen ions (nitrogen atoms with one electron removed).
All three images correspond to different shades of red light, so we enhanced the color differences to make the nebula’s delicate structures more obvious.
In this case, light from hydrogen atoms is shown in red, light from oxygen is shown in blue, and light from nitrogen is shown in green.

Note – A few years ago, I was asked to review Elizabeth Kessler’s 2012 book Picturing the Cosmos: Hubble Space Telescope Images and the Astronomical Sublime. The review came out in a fairly obscure academic journal with far less exposure than Kessler’s fine book warrants. With the 25th anniversary of the launch of Hubble this week, I wanted to present the review to a wider audience and make a few additional observations.

One can quibble about the details but the facts stand for themselves – the Hubble Space Telescope is the most influential (and certainly most expensive) science facility in human history. Its influence can be measured not just the number of scientific papers it has produced but also in terms of the global reach the images from HST have and the ways in which they have taken root deeply into the popular imagination.

The ways in which these images come to us are the subject of Elizabeth Kessler’s wonderful book Picturing the Cosmos. I encourage anyone who is fascinated by Hubble’s photographs and their impact on the visual imagination over the last quarter-century to pick up a copy.

Just writing that – a quarter-century – stands out. There is a generation of scientists now who literally cannot remember a time when there was no Hubble Telescope. The ways in which Hubble’s data is used and re-used have shaped astronomical practice. Look at this graph:

This image alone makes it clear how Hubble has changed the ways in which astronomers do their science. Somewhere around 2003, the number of publications using data from the HST archive surpassed those produced from actual observations. The number has continued to climb. And, today, something like 40% of HST-related publications use only archived data.

In 1998, the Hubble Heritage Team was preparing to release a new image of the planetary nebula NGC 3132. Hubble Heritage images appear not just in research papers but on calendars, coffee mugs, and the walls of art galleries. This is partly why HST is so influential…they literally shape how many citizens and scientists around the world see the universe. When describing how a balance between aesthetic inclinations and scientific veracity was found for the NGC 3132 picture, one team member explained, “We tend to look for things that ‘look right.’ And what exactly looks right is maybe a little hard to quantify.”

This quote come near the end of Kessler’s excellent and thought-provoking new book, captures a great deal of the tension inherent in making and viewing contemporary astronomical images. Such scientific images have an inherent aesthetic and artistic quality. As Kessler’s book reveals, they do all sorts of work besides “merely” conveying scientific information.

The “astronomical sublime” is central to Kessler’s analysis of Hubble images. Primarily focusing on the work of the Hubble Heritage Project, she expands on the sublime’s characteristics features (astonishment, the infinite, and even terror) and extends it beyond its origins with 18th century scholars like Immanuel Kant and Edmund Burke. Contemporary Hubble images not only reflect qualities of the sublime but also resemble earlier traditions in western art. We can compare Hubble images to famous 19th century landscape paintings by artists such as Thomas Moran and Albert Bierstadt.

Thomas Moran’s Cliffs of the Upper Colorado River, Wyoming Territory (1882)

The famous 1995 “Pillars of Creation” image – a view of the Eagle Nebula – has parallels to, for example, those the towering cloud and rock formations found in Romantic scenes of the American West.

These 19th century scenes of the American frontier once conveyed natural splendor to parlor-bound citizens. They also communicated the ideology of manifest destiny and the transformative power of the frontier as Frederick Jackson Turner famously noted. In similar fashion, images from Hubble reflect their own historical moment by stimulating public interest and continued funding for NASA’s continued exploration of the cosmic frontier. In the early 1990s, when the telescope’s initial spherical aberration threatened to undermine public and political support altogether, images from Hubble proved especially critical. They convinced scientists, politicians and tax payers that a hobbled Hubble could still produce good science and a repaired telescope even more so.

Kessler’s book blends the histories of art and astronomy with oral history interviews and observations of contemporary astronomers at work. She also engages with the work of other scholars who have considered the nature and use of astronomical images. The book, for example, finds common ground with Samuel Edgerton and Michael Lynch’s earlier work on digital image processing.1 Also critical are the ways in which astronomical images – especially the highly visible ones from the Hubble Heritage Project – perform functions besides those narrowly construed as “scientific.”

Look at this still from the 1990s show Star Trek Voyager – what’s in the background? A Hubble image.



Years ago I interviewed NASA administrator Ed Weiler. At the time, NASA was defending the budget for the James Webb Space Telescope (sometimes, but erroneously – I think – billed as the successor to Hubble). One of the things we talked about was the popularity of Hubble and how this helped sell JWST to a skeptical Congress. Weiler remarked – and I’m paraphrasing – that if he wanted to know which Hubble images were popular, all he had to do was watch Voyager (or check out the calendars and coffee-table books packed with Hubble images.)

Kessler’s treatment of HST images is far from naïve, however. Kessler explains how Hubble images are “doubly translated”, moving from object into digital data and then into image. This issue of conversion has long been an issue for astronomers. How a Hubble image is produced is as important as the image itself. Starting with proposal submission and moving to data collection, calibration, analysis, and presentation, we encounter persistent questions about the “objectivity” of scientific images. What constitutes a legitimate image when so much massaging and processing goes producing it? However, issues about authenticity existed long before the advent of digital images, starting when astronomical images were first captured via hand-made drawings and then recorded with photographic techniques.

At the same time, there is something profoundly different about digital images. New tools and standardized formats developed in the late 1970s and 1980s facilitated the circulation of digital data. Meanwhile,image processing technologies (derived from classified reconnaissance activities) gave scientists greater flexibility in using contrast, color, and cosmetics to interact with their data. Although positioned as “rational” depictions of the cosmos, Hubble images reflect aesthetic and personal choices consciously made by scientists as well as the technological legacy of the Cold War. If these ideas and images intrigue you, check out Kessler’s excellent book.

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Hubble, on the other hand, is the first and only space telescope to observe the universe using primarily visible light. Its stunningly crisp, colorful, and detailed images of the cosmos make Hubble a kind of supreme version of human eyes in space. Yet Hubble's appeal to us comes from much more than parades of pretty portraits. Hubble came of age in the 1990s, during an exponential growth of access to the Internet. That's when its digital images were first cast into the public domain. As we all know, anything that's fun, free, and forwardable spreads rapidly online. Hubble images, one more splendorous than the next, became screen savers and desktop wallpaper for computers owned by people who never before would have had the occasion to celebrate, however quietly, our place in the universe.

Indeed, Hubble brought the universe into our backyard. Or, rather, it expanded our backyards to enclose the universe itself. It did that with images so intellectually, visually, and even spiritually fulfilling that most don't even need captions. No matter what Hubble reveals—planets, dense star fields, colorful interstellar nebulae, deadly black holes, graceful colliding galaxies, the large-scale structure of the universe—each image establishes your own private vista on the cosmos.

Hubble's scientific legacy is unimpeachable. More research papers have been published using its data than have ever been published for any other scientific instrument in any discipline. Among Hubble's highlights is settling the decades-old debate about the age of the universe. Previously, the data were so bad that astrophysicists could not agree. Some thought 10 billion years. Others, 20 billion. Yes, it was embarrassing. But Hubble enabled us to measure accurately how the brightness varies in a particular type of star that resides in a distant cluster of galaxies. That information, when plugged into a simple formula, tells us their distance from Earth. And because the entire universe is expanding at a known rate, we can then turn back the clock to determine how long ago everything was in the same place. The answer? The universe was born 14 billion years ago.

Another result, long suspected to be true but confirmed by Hubble, was the discovery that every large galaxy, such as our own Milky Way, has a supermassive black hole in its center that dines on stars, gas clouds, and other unsuspecting matter that wanders too close. The centers of galaxies are so densely packed with stars that Earth-based telescopes see only a mottled cloud of light—the merged image of hundreds or thousands of stars. From space, Hubble's sharp imagery allows us to see each star individually and to track its motion around the galactic center. Behold, these stars move much, much faster than they have any right to. A small, unseen yet powerful source of gravity must be tugging on them. Crank the equations, and we are forced to conclude that a black hole lurks in their midst.

In 2005, the Bush Administration announced that Hubble would not receive the needed funds for this last servicing mission. Curiously, the loudest voices of dissent were not from the scientists but from the general public. Akin to a modern version of a torch-wielding mob, angry editorials, snippy letters to the editor, and no end of radio and television talk shows all urged NASA to restore the funding and keep Hubble alive. Congress ultimately listened and reversed NASA's decision. Democracy had a shining moment: Hubble would indeed be serviced, one last time. For the first time in the history of civilization, the public took ownership of a scientific instrument—they took ownership of the Hubble Space Telescope.
http://www.haydenplanetarium.org/tyson/ ... -of-hubble

Q: Has Hubble had more success in its role as a scientific ambassador than in its role as a scientific instrument?

A: You know, it's hard to measure those. How do you compare two superlatives? Hubble came around at a time when people were just getting email accounts and just learning about a World Wide Web. And so Hubble with its digital imagery was perfectly timed and perfectly poised to bring the public into its home. (It) enabled them to embrace all that Hubble saw in the universe.

http://www.usatoday.com/story/tech/2015 ... /25758381/

The nearly 20-year-old Hubble Space Telescope has taken many iconic images of the cosmos and is even the star of a new 3D IMAX movie that gives viewers a chance to fly through those snapshots. But does Hubble show us what the universe really looks like?

Yes and no, according to NASA.

When Hubble beams down images, astronomers have to make many adjustments, such as adding color and patching multiple photos together, to that raw data before the space observatory's images are released to the public.
Hubble doesn't use color film (or any film at all) to create its images. Instead, it operates much like a digital camera, using what's called a CCD (charge-coupled device) to record incoming photons of light.

Hubble's CCD cameras don't measure the color of the incoming light directly. But the telescope does have various filters that can be applied to let in only a specific wavelength range, or color, of light. Hubble can detect light throughout the visible spectrum, plus ultraviolet and infrared light which is invisible to human eyes.
The observatory will often take photos of the same object through multiple filters. Scientists can then combine the images, assigning blue light to the data that came in through the blue filter, for example, red light to the data read through the red filter and green light to the green filter, to create a comprehensive color image.

"We often use color as a tool, whether it is to enhance an object's detail or to visualize what ordinarily could never be seen by the human eye," NASA officials explain on the agency's Hubble Web site.
For some Hubble photos, such as the galaxy ESO 510-G13 for example, the end result is a close approximation of the colors people would see with their own eyes were they to visit the distant sight in a spacecraft.


Though even these photos are an enhanced version, since most celestial objects, such as nebulas, emit colors that are too faint for human eyes to make out. It takes a telescope, letting light build up in its CCD over time, to see the rich hues in Hubble photos.

And for other Hubble images, scientists assign colors to the filters that don't correspond to what that light would look like to human eyes. They do this when using light from infrared and ultraviolet filters, since those wavelength ranges have no natural colors, or when combining light from slightly different shades of the same color.

"Creating color images out of the original black-and-white exposures is equal parts art and science," NASA said.

For example, Hubble photographed the Cat's Eye Nebula through three narrow wavelengths of red light that correspond to radiation from hydrogen atoms, oxygen atoms, and nitrogen ions (nitrogen atoms with one electron removed). In that case, they assigned red, blue and green colors to the filters and combined them to highlight the subtle differences. In real life, those wavelengths of light would be hard to distinguish for humans.

The Hubble Space Telescope launched in April 1990 and has been visited by NASA astronauts multiple times for vital repairs, maintenance and upgrades.
The most recent visit was in May 2009, when astronauts performed five tricky spacewalks to add a new camera, spectrograph, and make unprecedented repairs and upgrades that left Hubble more powerful than ever before.
NASA scientists hope those upgrades will add at least five more years of life to the aging Hubble Space Telescope.

Harvey wrote:We only see a fraction of the available light so it's not a cheat, just rendering the invisible visible.

brekin wrote:

Harvey wrote:We only see a fraction of the available light so it's not a cheat, just rendering the invisible visible.

Sure, and if I sent you this photo of a tree outside my house and told you that this is what it looked like you would be totally ok with it? Because I was just trying to make some of the invisible visible for scientific reasons?

Harvey » Thu Apr 28, 2016 4:46 pm wrote:Yes, I like it.