The entry level into this pursuit need not be high if one is happy to photograph the Moon and the brightest planets with a digital camera - either the cheap fixed lens type or a digital SLR. Such objects should not be decried – there are some renowned amateur astrophotographers who photograph little else, even travelling to another continent to seek excellent “seeing” for high resolution photographs, albeit with specialised equipment. Although not ideal, a Dobsonian telescope can be used for lunar photography, as it is very stable and virtually vibration-free.

Apart from a telescope, a stable mount and a camera, all that is required is a camera adaptor. Both digital SLR and fixed-lens cameras are suitable for lunar and planetary photography. Suitable adaptors to connect the camera to the telescope are available commercially. (Check out advertisements in Sky & Telescope or on the Internet.) Because the CCD or CMOS chips in digital cameras are very efficient at collecting photons, exposures with such cameras will be short – in fact the challenge could well be reducing the brightness.

Camera adaptors are available that allow eyepiece projection – that is, using a normal eyepiece to magnify the image at the focal plane. Without magnification, images of planets are too small to be worthwhile. However, because magnification effectively increases the focal ratio, there are limits to what can be achieved without a driven mount. For example, a photo of Jupiter or a part of the Moon at f64 and with the camera set at ISO 400 would require an exposure of about ¼ of a second, but Saturn about 1 second, possibly resulting in a lack of sharpness due to trailing of the image. A very fast ISO rating (eg, 1600) will allow a reasonably untrailed image to be achieved, but the image could be "noisy".

The correct exposure can be achieved by trial and error or from recommendations in various publications that relate object, focal ratio, ISO rating and exposure time. However, it is not a simple matter to establish the focal ratio of an eyepiece projection setup. There is a formula that can be applied, but this needs knowledge of dimensions of not-easily-established elements of the optical system. Another way is to use photography as follows. First photograph the moon at prime focus. (It is assumed that the focal ratio of the telescope is known or can be readily established.) Next, photograph an area of the moon with eyepiece projection using each eyepiece in turn and print all images at the same scale. By measuring the distance between the same craters on the projected images, the focal ratios of the eyepiece projection setups can be calculated, as image size is proportional to focal ratio. Whether or not one knows the focal ratio for certain, it is still advisable to bracket exposures, as most subjects are not uniformly illuminated.

Another avenue to pursue – one not needing a telescope – is long exposure wide field photography using a tracking platform. The construction of such a device has been well described in numerous publications (eg Astronomy, September 1984) and on Internet sites and will not be attempted here. With careful use, good wide-angle photos of constellations using normal 35 to 105 mm lenses can be achieved with exposures of 5 to 10 minutes if the camera allows such exposures to be set. (This is usually the case with SLR cameras but not with fixed lens types.)