Your Own CCD for $100

Transcription

1 Your Own CCD for $100 Digital images with a web camera Introduction While surfing the Internet in late 2000, I came across quite a few sites that featured images of the sun, moon and planets that were made with the very simple "webcams" that are usually used for video conferencing. Having seen samples of images taken like this previously, I was aware of this possibility, but had never considered it an option for myself, as I believed the modification of such a device for astrophotography would be too difficult for me. However, the web sites I visited led me to believe otherwise. One web site (a compilation of links is featured at the end of this article) compared the best camera for a beginner to buy. It appeared that the most popular webcams for astro imaging are the Logitech "QuickCams", originally manufactured as a simple B&W computer camera by Connectix. Meanwhile, there are several models, ranging from simple webcams to complex video devices that can do everything from video conferencing to video surveillance. Of all of these, the QuickCam VC was the recommendation for starting in webcam astrophotography. [Note: today (2002), the ToUcam Pro is generally considered the best webcam for astrophotography.] QuickCam VC The CCD (Charge-Coupled Device) is a fascinating tool imaging the night sky. The ability of taking as many images as the hard disk of the PC you are using will hold, viewing these images in real-time, and being able to combine as many images as you want in order to increase the signal-to-noise ratio offer great advantages for planetary as well as deep-sky photography. The high sensitivity of a CCD as compared to traditional film means that deepsky exposures last from several seconds to a few minutes, while it allows the user to "beat the seeing" when imaging the Moon and planets. Last, but not least, the ability to store images on a computer directly means a tremendous decrease of costs for film and (1 of 12)4/28/2006 7:58:28 PM

2 processing, which usually exist when photographing planets with film. Phase One Unfortunately, even entry-level CCD cameras that are actually built for astro imaging are beyond the reach of many amateurs. I faced the same problem. A QuickCam, however, costs approximately $70 if bought in a store, much less if you are buying a used camera at a flea market or through online auction sites like ebay. Here, it is possible to find the older B&W QuickCam, which is not manufactured anymore, but is much better suited for astro imaging than the other webcams. However, as I did not want to search for a used B&W camera first, I spontaneously bought the QuickCam VC from a PC supplier through the Internet. Three days later, a package arrived containing my new toy. Splitting the halves of the egg-shaped casing proved to be more difficult than I had expected, and I rather destroyed it in the process. But the casing was not important; I wanted the circuit board with the CCD chip. The first step to making your QuickCam astro-compatible is to remove the lens, which in the case of the QuickCam VC is done by unscrewing the lens from its mount. What is left can be seen below: For a temporary solution, you can replace the circuit board in the egg casing (without the lens, of course), and snap the two halves together again. In order to place the camera at the prime focus of a telescope, I glued an empty film can with part of its top cut out and its bottom completely removed to the QuickCam's casing (see images below). (2 of 12)4/28/2006 7:58:28 PM

3 The film can has almost exactly the outside diameter of an eyepiece (Fuji film cans fit best), and the camera can thus be inserted into the eyepiece tube of the telescope. Using the default software included with the camera, I started trying out different brightness and contrast settings for different objects. The camera at the prime focus of a 1250mm telescope delivers quite highly magnified images, as the CCD is very small compared to 35mm film and thus produces a large image scale. (3 of 12)4/28/2006 7:58:28 PM

4 This is my first image taken with the webcam in this phase of the modifying process. The image was taken from inside my room, as the webcam's cable is only a few feet long. Thus, a lot of turbulence resulted from the very warm air in my room and the very cold air outside my window. In addition, the Moon was almost completely washed out by haze. Nevertheless, quite a few features are visible. My hopes were high that a lot could be achieved with this webcam... Phase Two Unfortunately, the film can made the impression of being ready to fall off any moment, and my poorly opened QuickCam casing did not look very aesthetically pleasing, either. Therefore, I placed a quick order at my electronics supplier and ordered a small project box which would serve as the new casing for my CCD camera. The first thing I did was to screw a T2-ring to the project box in order for me to attach either an eyepiece projection adapter or 1 1/4"-adapter, as seen in the next photo. (4 of 12)4/28/2006 7:58:28 PM

5 Once again, I took apart the egg-shaped QuickCam casing and removed the circuit board. This has a black mount screwed onto it, which serves as a lens holder. As I had already removed the lens, this had no function, but was not destined for the garbage bin. I removed it from the circuit board and, after drilling a hole in the front of my project box, glued it to this hole with "Crazy Glue", sealing it off with silicone glue (below). After this step, it was possible to simply screw the PCB back onto the lens mount, thus having the CCD nicely positioned behind the opening in the front of the casing, as shown in the photos below. (5 of 12)4/28/2006 7:58:28 PM

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7 This picture shows the adapter setup for the phase two modifications. In this phase, the camera is in a new project box which has an T thread at the front. It is possible to attach either an eyepiece projection setup or a 1 1/4" eyepiece tube adapter (with optional barlow lens) to this for projection or prime focus photography, respectively. Phase Three As my laptop was not operational at the time I finished working on phase II, I could not take any images with the camera outdoors. Therefore, I continued searching the web for more ideas on what to do with my QuickCam. A very obvious thing to do was cooling the CCD, or at least the electronics surrounding it, because these tend to get quite hot, which results in noise in the images. There are many exciting ideas from Peltier modules to cooling with CO 2, but I chose a much simpler one. S.J. Wainwright, a master of QuickCam Astroimaging, suggested cooling the camera with an ordinary PC cooling fan. The idea behind this is for the fan to blow cool outside air into the project box, which lets the camera's operating temperature drop from about 30 degrees C to less than 10 degrees, depending on the outside temperature. Of course, cooling will be more efficient on a cold winter evening than in a summer night. A problem that may result with a fan is the a slight vibration of the camera, which would smear images. A quick correspondence with Mr. Wainwright, however, resulted in the assurance that he had never had problems with vibrations. In any case, the inclusion of a small switch on the outside of the casing would allow for the fan to simply be switched off. After drilling a hole for the fan and installing it, I drilled three other holes for the air to leave the camera again after cooling the CCD. The result is shown in the images below. (7 of 12)4/28/2006 7:58:28 PM

8 Success! I had finally managed to finish the modifications to the camera and have my own functioning astronomical CCD camera: (8 of 12)4/28/2006 7:58:28 PM

9 Here are some images of the camera connected to my scope, a Meade ETX mounted on a Vixen New Polaris german equatorial mount: (9 of 12)4/28/2006 7:58:28 PM

10 After my laptop finally arrived from the repair shop with a new hard disk, I used the first cloud break to shoot some images in the unstable air. To my surprise, they're not all that bad! (10 of 12)4/28/2006 7:58:28 PM

11 These images were all taken through the Meade ETX (focal length 1250mm, f/13.9). Note the moon to Jupiter's lower left (I don't know which one it is). Finally, a comparison of the advantage of CCD over film. The bottom right image is a raw scan of a film image. The left image is the result of stacking approx. 20 scanned film images and sharpening the result. This was more than an hour's work, not counting the time for taking the pictures. In addition, the costs of the film and developing need to be considered. The top image is a stack of 80 images obtained within a minute. Total work: 10 minutes, cost: none! Conclusion Experimenting with a QuickCam for astrophotography seems to be a lot of fun. If you like playing around with basic electronics and like building stuff, it's an ideal project, especially as quite rewarding results can be achieved with very little effort and, most importantly, a very small budget. A gallery of images obtained with this and other webcams can be found here. Resources (11 of 12)4/28/2006 7:58:28 PM

12 Astrocam - French/English website, very complete with modification instructions, image galleries and links to more images and software (special QuickCam drivers, image processing) QCUIAG - QuickCam and Unconventional Astronomy Imaging Group, modification instructions and tips, image galleries> Vega - Image capture program for use with the QuickCam AstroStack - Did you take 160 images of the Moon and don't want to stack them manually? This program will do the work for you - a great resource! Back (12 of 12)4/28/2006 7:58:28 PM