Most every person who owns a telescope gets the itch to take a photograph of what they see sometime during their astronomy life. This is a very simple task with the use of a telescope and a camera lens. Tracking stars takes long exposures, specialized skill, and some equipment. Taking more colorful photographs of “star trails” or of the northern lights is something any hobbyist can do. If you already have a telescope and camera with lens, all you need is a camera adapter for the telescope. There are many common ways to use a telescope and camera lens in combination for astrophotography.
Camera on Tripod
Piggybacking the camera
Afocal Projection
Prime Focus
Eyepiece Projection
Camera On The Tripod
With this method your telescope and camera lens are separate. You use a “normal” or “wide-angle” camera lens. The telescope finds the shot and exposure time of the camera gives you a star trail, or very bright stars with little movement. Pointing the camera north or south gives a curved star track. This method is great for capturing the northern lights. Using a cable release to trip the camera shutter keeps the setup from shaking.
Piggybacking
If you have the ability to track the stars in equatorial mode on your telescope, your camera lens can easily be attached to the outside of the scope. This would be a long exposure photograph of ten minutes or longer, like the star trails. The difference is that the telescope moves the camera lens to counteract the earths motion while keeping the stars in place. Using the telescope and various camera lenses years worth of astrophotographs can be obtained with piggybacking. For people who do not have a tracking telescope, there is a device called a “Barn Door Tracker” which can be built to track the movement. You would need a camera adaptor for your telescope to use this method.
Afocal Projection
With Afocal projection, both the eyepiece of the telescope and camera lens are used. The camera focus is set to infinity and simply held up to the eyepiece. This is the ideal way to get moon shots or pictures of the sun. This is also the most effective method of the telescope/camera lens combination when using a digital camera. For cameras using film, different shutter speeds are required to find the proper exposure for this method.
Both Prime Focus and Eyepiece Projection are more specialized telescope and camera lens combinations which can require more equipment and much practice to achieve good results with. For beginners, the three methods listed in this article will give you a wide range of practice and good variety of photographs.