Jeff Terry
Capturing Light from Long Ago
iCCD works best when you apply the Mac’s processing power separately from the Luminance data (black-and-white), then the RGB data (color).
Astronomical photographic targets fall into two categories, more or less, and there is a different approach to capturing each of them. The first type of targets — relatively close up, small, bright bodies with surface detail (such as planets or Earth’s moon) — are generally shot with video cameras (often web-cams) at many frames per second. The object is to capture many pictures quickly, before the planet rotates or moves and then select the clearest frames. There can be hundreds of images to combine or choose from. With such targets, iCCD is a huge help in cleaning up the chosen frames and combining them seamlessly.
The second target type includes nebulae, galaxies, and star clusters, which tend to be relatively far away, spread out, and diffuse. These dim objects require long exposures (minutes or hours) with purpose-built cameras that use active cooling to greatly reduce the “self-noise” endemic to CCD devices. iCCD’s power facilitates stacking dozens of long exposures, automatically combining and “de-noise-ing” them.
Terry and other experts believe that deep sky targets are best nabbed by shooting their weak light in separate frequency bands (i.e., colors), which requires individual filters — usually Red, Green and Blue — across the telescope’s aperture or just before the CCD detector. iCCD can control CCD cameras equipped with built-in filters. It’s also vital to shoot one image with no filter or with a filter optimized for black-and-white. This is called the Luminance frame.
Terry wants iCCD users to spend most of their time on the Luminance frame because the eye isn’t nearly as sensitive to color as it is to variations in brightness. So garbage isn’t revealed in the color data by cleaning up noise in the Luminance information. Terry even created a Digital Development “one-click-to-fix” routine that automatically corrects the picture.
Pretty Pictures and Hard-Core Science
Students often export final, cleaned-up images to Adobe Photoshop for resizing and output to JPG or other formats. But they get a big cautionary flag from Terry. As soon as they leave the realm of iCCD and venture into other graphic-production environments, they’ve departed from true science data and entered the kingdom of pretty pictures. Terry believes there’s nothing wrong with making beautiful images — as long as they are clearly identified as such in scientific circles. In working with astronomical image manipulation, his students learn firsthand how to keep the line between data and interpretation clean and pure.
Cocoa and Objective-C made it easy for Terry to build advanced sets of digital filter processing commands into the menus of iCCD.
It’s difficult to get snapshots of infinity when, as Terry puts it, “you’re dealing with blue screens of death.” Imaging the universe also calls forth something that engineering students are not often formally trained to deal with — profound and deeply personal philosophical investigations into our place in the cosmos. But it’s difficult to attain this level of thought if you’re fighting with a cumbersome interface, struggling to de-convolve your image stack, or surfing to find the most recent driver download.
Terry chose the Mac for iCCD (and he works to constantly improve his application) because he wants to spare astronomy visualization enthusiasts annoyances like these. This sense of community on the part of Apple and those who develop Mac OS X applications may ultimately be the biggest reason that scientists, and astronomers in particular, gravitate toward the Mac.
The most pressing issues in astronomy and astrophysics focus on how life began, how common it is, what environments and evolutionary processes led to intelligence, what the beginning of the universe was like, and how will it end. These are, as Carl Sagan called them, “deep, deep questions.” And Jeff Terry doesn’t mind losing any sleep over them.
