Guide to cheap astrophotography

Imaging methods explained

There are several ways to take photographs of the sky, the methods vary in complexity, skill required, cost of equipment and of course type of image produced. Any that require a telescope can be done with a reflector, refractor or indeed any type of scope as long as it has removable eyepieces.

Wide field

Wide field astrophotography can be as simple as pointing a camera at the sky and pressing the button. Normally a tripod would be used and some method of setting long exposures. For extremely long exposures some sort of tracking is needed otherwise the stars will form trails as they move relative to the earth. This is a great way to start as it can initially be very inexpensive and gives you a good idea of where the stars are and how to find them. As long as you can find a wall or stable surface, and your camera can do long exposures (or has a night mode) you will be able to get some shots. You should use a shutter delay setting or remote control if you have one to avoid the button press from moving the camera. The camera can either be mounted on a standard photographic tripod (or mini tripod), a telescope style tripod, or attached to the top of a telescope using a method called piggybacking.

A more experienced widefield photographer can get some stunning and extremely rewarding images.

Afocal

This method involves holding the camera (with its lens) up against the telescopes eyepiece. Either by hand or by using some kind of mechanical mount. Most mounts clamp on to the eyepiece and screw on to the bottom of the camera (£20-£40). This is basically taking a photo of what you would see with the eye. Its a great way of adding imaging to your astronomy hobby. Its very cheap to get started if you already have the telescope and a camera as basic as the one on your phone can still give rewarding results.

Prime focus

Prime focus astrophotography is achieved by basically attaching the telescope to the camera in place of its lens, for this reason a camera with removable lens is required, such as a dSLR, SLR, or some of the newer bridge cameras that have removable lenses. No eyepiece is used in the telescope and the cameras lens is removed. The camera body attaches directly to the telescopes focuser tube and the image from the telescopes primary mirror (or lenses for a refractor) is formed directly on to the cameras sensor chip. For dSLR's this will normally be achieved by using a T mount adapter for your specific camera model (£10-£15), and then a T mount to telescope adapter (£15-£20). This has the benefit of the minimum number of bits of glass between the cameras sensor and the object your imaging. This increases the sensitivity and therefore the amount of detail you can expect in your images. As there are no lenses involved there is no way to alter the magnification other than digitally afterwards.

Eyepiece projection

This method is similar to Prime Focus apart from the fact it also uses the telescopes eyepiece. An adapter is fitted to the telescope, inside this adapter a standard telescope eyepiece is inserted. Attached to the end of this adapter is the camera body, WITHOUT its lens. This method has the benefit that you can vary the magnification by choosing different eyepieces.


Another form of astrophotography to consider is using a camera with a very large telephoto lens. But as technically this large lens could be considered a telescope in its own right it is basically a form of prime focus photography.