WHAT'S UP: Astro-photographs are like nothing you’ve ever seen

Jun 3, 2011

 

Although Hancock may be described as “amateur” (if I were talking to you about this, I would be making air quotes with the middle and index fingers of both my hands, a gesture my 8-year-old son has mastered) because he doesn’t earn his living taking pictures of heavenly objects, there is little about his astro-photographs that are amateurish.

Hancock’s pictures of stars, galaxies and nebulae are beautiful; they are the product of thousands of dollars of equipment, years of experience, and hours and hours of patient photographing and digital image processing.

You can view Hancock’s work and learn about his methods at the website he maintains: www.downunderobservatory.com. He hails from Australia, where he lived until 2001 when he moved to Michigan.

Photographs of faint celestial targets show them in detail that can never be seen with the eye — even through the most powerful telescopes.

Our eyes and the visual center of our brains are like video cameras: They form moving images in real time, stitching together still snapshots at a rate of about 30 frames per second. Between each frame, our imaginative brains fill in a great many details.

Just how much detail our brains imagine is apparent if you watch a DVD movie in super-slow motion, manually stepping through each motion-blurred frame of the movie. Action scenes work the best.

While our visual system serves us well for catching the hint of movement out of the “corner of our eyes,” in the periphery of our view in a well-lit environment, it leaves us in the dark when we try to see something faint.

Our visual system cannot stop producing images at 30 frames per second. It does not allow us to stare deeply into the dark for a long period of time and accumulate light until faint, wispy detail stands.

A still-image camera can record scenes we can never see because, in a skilled photographer’s hands, a camera can be set to open its eye and leave it open until a bright image has been recorded of even the faintest scene.

It’s not surprising that astronomers began trying to take pictures through their telescopes not long after the first cameras were invented.

The daguerreotype process — the first way of recording faint, fragile, monochrome images on metal plates — was invented by Frenchman Louis Daguerre in about 1835. In 1840, a first blurry and confused image of the moon was recorded through a telescope.

Pioneering astro-photographers had to overcome many problems in order to produce images with fine detail; the same problems contemporary astro-photographers have to overcome.

The most demanding problem is keeping a telescope/camera pointed at its target without even the tiniest deviation as the target moves across the sky, owing to Earth’s daily rotation. Even image jitter caused by the atmosphere blurs astro-photographs, and the blurring is more pronounced for longer exposure times.

It wasn’t until the 1850s that astronomers were able to record detailed images of the lunar surface and of the brightest stars in the sky, and then not until the 20th century that they were able to image faint galaxies and nebulae.

Modern astro-photographers like Terry Hancock overcome the tracking and blurring problem digitally. They take a large number of medium-duration digital images and align, add them together, and colorize them using software (like Photoshop).

Hancock’s images — some the result of more than six hours of exposure time — are like nothing you’ve ever seen.

— By Doug Furton, who is a member of the physics faculty at GVSU. Send questions and suggestions to dgf@inbox.com. An archive of some of his “What’s up” columns is available online at gegenschein.wordpress.com.

 

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