Jeff Terry

Capturing Light from Long Ago

By Dave Brody

Thanks to Apple’s vImage technology, iCCD can resolve bright objects, like this comet, along with subtly colored objects, like the m57 Ring Nebula.

Jeff Terry doesn’t sleep much. That's because the Illinois Institute of Technology (IIT) professor of physics and his students spend their nights collecting dim light from faraway stars. A Mac mini attached to Terry’s research-grade telescope collects the raw data. Then an Intel-based iMac and a MacBook Pro squeeze the most science — and aesthetic beauty — from the light that trickles, one photon at a time, out of the deep past. When you’re on a mission to open up the universe for engineering and science students, sleep is a low priority.

Terry’s students don’t learn by simulation or by running scripted exercises. They do real science, even as they learn the necessary hardware and software engineering, creating detailed portraits of celestial objects by capturing photons from deep-sky objects in the distant universe.

“The Mac is a better visualization tool. It has always done graphics at a much higher level than other platforms.”

The Charge Coupled Device (CCD) cameras Terry’s team uses to capture photons, the most basic units of electromagnetic radiation, must be placed outside — often in the bitter cold. CCDs work best under clear, dark skies, far away from the sky-glow of cities. Such environments often aren’t user-friendly, so Terry decided to create his own software that would not only automate many of the hands-on camera- and telescope-management tasks, but also handle the specific demands of astronomical image processing. The result is iCCD, a free, downloadable program that helps shoot images of a wide range of astronomical objects and makes processing those images instinctive and easy.

Terry knew the science — and the craft — of making astronomical photographs. But until he created iCCD, no Mac-based tools were available for processing astrophysical images. Terry has long preferred the Mac platform’s strong picture-handling abilities and intuitive interface, so he chose Mac OS X for his development platform.

“The Mac is a better visualization tool,” he says. “It has always done graphics at a much higher level than other platforms.” Terry found it easy to create his unique code using Apple’s Objective-C object builder, Xcode integrated development environment, and Cocoa graphical user interface maker. He also found a wide mix of helpful visualization professionals within the Mac community.

With integrated menus that focus the telescope and camera, guide the telescope, choose filters, and specify the number of frames to be shot, it is much easier to get accurate, clean scans of the sky with iCCD than with similar software. “It’s not uncommon to collect 5GB or 10GB of images in one night,” Terry says. So he has also built image library management and metadata tagging into iCCD’s GUI.

Piling Up Pictures

But acquiring raw images is just the first step. Creating an accurate astronomical picture often requires stacking several exposures of one region of the sky. This approach produces the cleanest pictures because, although each frame might contain errors, stacking them — i.e., taking their average — cancels out much of the noise. iCCD makes this stacking process easy, with just a few menu-driven commands that initiate intelligent automated procedures. Tweaking layers further improves the images by extracting the maximum useful information while suppressing camera artifacts, killing falsely bright pixels caused by transient cosmic events and quieting electronic circuit noise.

iCCD could be the beginning of a revolution in Mac-based astronomy. Not every telescope has its own Mac interface. But most go-to-style telescope mounts can be piloted by X11 (X Window system) protocols. Terry likes the fact that Macs can run UNIX programs with a fairly easy recompile. As a result, most telescopes can be controlled by using the same Mac desktop that runs the iCCD-managed camera.

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