The moon shone brightly above my home-built observatory one pleasant midsummer evening last year. Approaching first quarter, it was the subject of an experiment. My jaw dropped as the lunar scene came to focus on the computer's screen - I wasn't prepared for the clarity and resolution. I sat mesmerized by the view from the tiny CCD camera on my telescope. The Alpine Valley was a beautiful sight as were the crater Cassini and the isolated peak Piton. Even the subtle wrinkle ridges on the basaltic floor of Mare Imbrium were etched clearly into the image.
Reaching for the hand controller, I began steering the telescope around the lunar highlands and along the terminator. With the help of a lunar atlas illuminated by the glow from the computer monitor, I identified scores of features as they scrolled across the screen. It was as if I were living a childhood dream and flying over the Moon's alien landscape.
First light with any CCD camera is exciting. But my experience was all the more remarkable because my new camera was a Connectix QuickCam purchased by mail order for about $60 and modified for use on my telescope. It is capable of making stunning images of the Moon and surprisingly good ones of the bright planets. Some of the results compare favorably with those from CCD cameras costing hundreds of dollars more.
Only a year earlier a growing interest in astronomy led me to purchase a Meade 8-inch LX50 telescope. Because I wanted a solid base for astrophotography and CCD imaging, during the subsequent winter I pondered the idea of a backyard observatory. With inspiration from Rob West's article in this magazine's May 1997 issue and my father's help, I completed Lance Hill Observatory in June 1997. The 8-by-10-foot structure with a sliding metal roof is nestled in the channeled scablands and ponderosa pines of eastern Washington State a few miles southwest of Spokane.
While the building was under construction I began searching the World Wide Web for information on CCD cameras. Discussions on the sci.astro.amateur newsgroup led me to the Connectix QuickCam. I quickly realized that this simple, black-and-white camera might be a fun, creative, and inexpensive introduction to CCD imaging.
The QuickCam easily connects to any Macintosh II computer or an IBM-compatible PC running Windows. It can capture video and still images with up to 64 shades of gray (6-bit images) in a 320-by-240-pixel format. It attaches to a PC's parallel (printer) port and is powered by an additional connector to the mouse or keyboard cable. With a Macintosh II the QuickCam connects to a serial or modem port. The camera comes with a 6-foot cable, but some people have increased this to as much as 15 feet with extension cables.
The QuickCam is based on the same Texas Instruments TC-255 CCD chip found in many high-quality astronomical cameras such as Celestron's PixCel 255, Meade's Pictor 208XT and 216XT, and SBIG's ST-5. The chip's 10-micron-square pixels form an imaging area measuring 3.2 by 2.4 millimeters and provides a field of view spanning 5.4 by 4.0 arcminutes at the focus of an 8-inch f/10 telescope. At this focal length each pixel covers 1 arc-second of sky, which is good for imaging the Moon and planets. Unlike cameras designed specifically for astronomical work, the QuickCam's CCD is not cooled and is thus limited to exposures lasting no more than a few seconds. The camera is not suitable for deep-sky imaging.
The camera's software is fine for capturing views of the Moon and bright planets, and upgrades to the program's latest version are available from Connectix Corporation's site on the World Wide Web (see page 120). The Windows interface includes the active image area, a menu bar, and a slide bar to adjust brightness. The software can create image files in BMP, TIFF, and JPEG formats. A full-resolution BMP file occupies about 77 kilobytes of disk space.
The image quality and camera settings are modified by clicking on the menu bar. You can select quarter-, half-, or full-frame images with either 16 or 64 shades of gray. The brightness, contrast, and white balance can be adjusted independently. Modifying these settings instantly changes the image displayed on the computer monitor. Optimum exposure is automatically determined; just click on the "Take Picture" button when you see what you want to capture on the screen. The image is automatically saved to disk.
The QuickCam software does not include routines for dressing up the images after they are taken, but this can be done with other image-processing programs. Nor does the camera allow pixel binning or handle antiblooming (streaks on images due to overexposed pixels) as do some sophisticated astronomical cameras.
Adapting my QuickCam for astronomical work required a few hours' effort. I began by carefully dismantling the camera following the excellent instructions posted on the World Wide Web by Hanno Muller (see the box on page 120). Others who do this should keep in mind that opening the camera voids the manufacturer's warranty. The key to taking the QuickCam apart is the hole underneath a piece of tape on the rear of the camera. Pushing a small screwdriver into this hole releases two clips and allows the housing to be gently pried apart. Two other clips need to be disengaged during the opening process. Be especially careful of the fragile black plastic frame around the lens - it can crack if one is overzealous when separating the camera's halves.
With the camera housing open, the circuit board, CCD, and lens simply slide out. Before handling the exposed electronics you should discharge any static electricity accumulated on your body by grounding yourself. The entire lens assembly and infrared-blocking filter are removed from the circuit board by loosening two tiny screws on the back of the board. With the lens removed you can see the CCD chip.
As shown in the pictures here, I mounted the circular circuit board and unobstructed CCD on the end of a plastic cap from a can of aerosol shaving cream. I used the same screws that held the lens assembly in place. The cap conveniently snaps over the T ring of my telescope's camera adapter. To have the CCD on the scope's optical axis it must be positioned at the center of the plastic housing.
Imaging with the QuickCam
The typical imaging session starts when I open the observatory and power up the telescope and computer. The QuickCam is connected to the parallel port of my 486 laptop. I also have an external VGA monitor attached to the computer.
I center the Moon or a bright planet in the field of a conventional eyepiece and then switch the eyepiece for the QuickCam assembly. While my camera isn't exactly parfocal with the eyepiece, it is close enough to allow centering the target on the CCD. Once the object is visible on the computer monitor, I slowly focus the telescope while watching the image, which automatically refreshes on the screen about once a second. My best views of the Moon are always found near the terminator, where the contrast is greatest and the relief accentuated.
I spend time manually adjusting the camera's brightness setting, which allows the software to automatically determine the proper exposure time. I usually take a dozen images of an object, hoping that several will be during those split-second moments of good astronomical seeing.
The images are copied onto floppy disks for transfer to a desktop PC. I use LView Pro to lightly process them with a sharpening routine and sometimes adjust the contrast before converting them to JPEG format for posting on my Web page.
In the future I plan to experiment with increasing the telescope's magnification for planetary imaging through eyepiece projection. I also want to experiment with filters for enhancing planetary details. Connectix makes a color version of the QuickCam, which might be interesting to modify for astronomical use. But it costs nearly $200 and you'd have a lot more to lose if it were to get damaged.
Transforming a black-and-white QuickCam for use on a telescope can be an exciting and creative experience. There is plenty of room for experimentation. I particularly hope that teachers find this inexpensive project an inspiration and use it to involve students with observational astronomy.
World Wide Web Resources
A growing number of sites on the World Wide Web include information helpful to those using QuickCams for astronomical imaging. A selected list appears here. Additional sites as well as links to all of them are available at SKY Online, http://www.skypub.com/.
Lance Hill Observatory http://www.geology.ewu.edu/jpb/lho/lho.htm The author's site includes images, links, and advice on using QuickCams for astronomy.
Connectix Corporation http://www.connectix.com The QuickCam manufacturer's site.
QuickCam Hack Web Page http://www3.gamewood.net/astronomy/ccdinfo/qc/ Information about mounting a QuickCam to a 1 1/4-inch telescope adapter.
Hanno Muller's Developer Resources http://www.kabel.de/hmueller/qc/ Excellent instructions for disassembling the QuickCam.
QuickCam Astrophotography http://ourworld.compuserve.com/homepages/chas_wray/ This page shows a nicely engineered housing for a modified QuickCam.
QuickCam Images http://www.geocities.com/CapeCanaveral/Lab/4171/qc.html Pictures of any by a modified QuickCam.
JOHN P. BUCHANAN is a professor of geology at Eastern Washington University. His research interests involve mapping large cave systems during the day, but at night he usually emerges to work in his observatory. You can send him e-mail at firstname.lastname@example.org.
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|Title Annotation:||using the Connectix QuickCam digital camera for moon-viewing|
|Author:||Buchanan, John M.|
|Publication:||Sky & Telescope|
|Date:||Jun 1, 1998|
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