Imaging the Moon

Great lunar results can be obtained using digital cameras. If you haven’t tried to photograph the Moon with your digicam or mobile phone held up to the telescope eyepiece, give it a go — you may be pleasantly surprised at the results.

Digital cameras capture light using the CCD (charge coupled device) a small flat chip – about the diameter of a match head in most commercial digicams – made up of an array of tiny light sensitive elements called pixels. CCDs in very low-end digicams may have an array of 640 x 480 pixels, while a more expensive digicam CCD may boast 12 megapixels.

Light hitting each pixel is converted to an electrical signal, and the intensity of this signal directly corresponds to the brightness of the light that struck it. This information can be stored digitally in the camera’s own memory or transferred to a PC, where it can be processed into an image. Digital images are infinitely easier to enhance and manipulate than a conventional photograph in a photo lab darkroom.

Digicams, digital camcorders, webcams and dedicated astronomical CCD cameras have enabled amateur astronomers with quite modest equipment the opportunity to obtain wonderfully detailed images of the Moon. Indeed, just about anyone can take an acceptable lunar snapshot by pointing a digital camera through a small telescope. It’s one thing to capture an image of the whole Moon showing features along its terminator, but it requires considerable skill and expertise – both in the field, and later at the computer – to produce a high resolution, close-up image of the Moon capable of impressing a seasoned lunar observer. Digital imaging devices are not all identical to use – for example, afocal digicam imaging requires different techniques to imaging the Moon with a webcam and Barlow lens at prime focus.