PHOTOGRAPHING COMET HALE-BOPP

Stephen J. Edberg, Jet Propulsion Laboratory

It is not difficult to photograph a bright comet such as Hale- Bopp. Simply mount your camera on a tripod, aim at the comet, and use a cable release to smoothly trip the shutter without jarring the camera. The camera should be focused at infinity and have fast film in it, ISO 800 or faster. Once the picture has been composed, with foreground objects if desired, the shutter is opened for a time exposure.

A camera with adjustable automatic or manual controls is not entirely a necessity but it is helpful. An adjustable camera should be set up with the lens opening at its widest and the shutter set on "B" or "T" so that it will stay open as long as desired. The shutter should be held open for 10 seconds or more.

For a camera lens whose focal length is 50 mm this exposure time will show no significant star trailing (due to Earth's rotation). Longer exposures will start to show trailing, though even 20 seconds will not be detrimental. Note that lens focal lengths longer than 50 mm will show trailing sooner while shorter focal lengths can have the shutter open longer, in an inversely proportional manner: a 100 mm focal length lens should use 1/2 the shutter time that a 50 mm lens uses, while a 28 mm lens could be open for 5/3 the shutter time for a 50 mm lens.

An automatic camera can also be used, though the results are not as certain. Use the highest speed film available (ISO 3200 can be found at camera stores). Mount the camera on a tripod and trip the shutter as gently as possible. If at all possible, shut off the automatic flash (or cover it with black electrical tape, unless you want the foreground illuminated, perhaps glaringly so). Most automatic cameras will sense the low light level in the field of view and the high speed of the film. The electronic brain in the camera will keep the shutter open for a longer than usual time, which will help in capturing an image of the comet. Check the owner's manual for hints on making successful low light photographs.

Good Luck!

Good Luck!