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I took the pictures for this article on a CCD camera that I attached to my 6" Newtonian. That, you might say is nothing out of the ordinary, as anyone can buy a CCD camera for X hundred pounds, hook it up and take pictures of bright objects. The difference in my case was that the camera was bought for the princely sum of $49, about the same as a cheap eyepiece. To be fair, I had to pay almost as much again in courier postage and import taxes, but it still worked out to be pretty cheap. The camera in question is Connectix QuickCam, available widely in the USA (I bought mine on the Internet). Its specifications are 320 x 240 pixels, with a 6 bit (64 level grey scale) digitising accuracy. The camera as it comes consists of a 2" (~50 mm) plastic ball, with a lens in the front, and a cable to attach it to your PC parallel port. My PC is an old 486DX66, so is no great shakes compared to modern machines, but copes quite well with the camera. You get a CD with all the software to take still pictures and also movies (although this eats up your hard disk !). I followed instructions given in a Sky & Telescope article (June 1998, pages 120 - 123) on dismantling the camera - very straight forward, and put it on the telescope. Jupiter was the first target, and I got a good image of the cloud belts with the camera at prime focus (I hope to try eyepiece projection when Jupiter is visible again later in the year). The results are seen in fig. 1.
Using the sharpening function in Paint Shop Pro, a slight improvement can be seen in fig. 2.
The contrast can also be stretched to show the differences in contrast between the North and South equatorial belts and the lighter equator as seen in fig. 3.
The stretched contrast image can then be sharpened as well, enhancing the image quality. This is seen in fig. 4.
In order to obtain images of the moons, it is necessary to over-expose the planet itself. I have not explored obtaining images of fainter objects very much so far.
Turning to the moon, I took a series of images making up a mosaic, the results of which are seen on page 4 of this issue of ARIES. As each image in the mosaic is 77k, the total picture of ~25 gets quite large. The alternative solutions to the space problem are to save in a compressed format (such as JPEG) or to buy a bigger hard disk or ZIP drive ! Fig. 5 is not processed at all, however processing can be used to enhance specific features, such as those on the terminator.
Important aspects of imaging with a CCD are focussing and pointing. The focussing bit is relatively straightforward, as the picture is displayed on the screen in (approximately) real time. Pointing is a different matter though, as the field of view is very small (the imaging area of the CCD is only 3.2 x 2.4 mm). I would recommend the moon as an initial target, as you can get some of it on the screen, and then move it around. It helps a lot to have slow motion controls, preferably electric, to position objects while watching the screen. My experience is that the mounting shows up its weaknesses very quickly !
I would encourage anyone who is tempted to get on the Internet (there are lots of Internet Service Providers with no subscription now…) as there a number of sites featuring QuickCams in an astronomical set-up. It does help to have a fast modem though if you are downloading lots of pictures !
If anyone wants to take a look at my camera before taking the plunge and spending hard earned cash, do give me a call on a clear evening with a moon or planet visible in the South.
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