Stars from a fixed tripod

Now for the stars. On a starry, moonless night, put the camera on a sturdy tripod, aim at a familiar constellation, set the aperture wide open, focus on infinity, and take a 10- to 30-second exposure at ISO 400 or 800. You'll get something like Figure 4.5 or Figure 4.6.

For this project, a 50-mm f /1.8 lens is ideal. Second choice is any f /2.8 or faster lens with a focal length between 20 and 50 mm. Your zoom lens may fill the bill. If you are using a "kit" zoom lens that is f /3.5 or f /4, you'll need to

Figure 4.3. The Moon, photographed by holding a Canon Digital Rebel (with 28-mm f /2.8 lens wide open) up to the eyepiece of an 8-inch (20-cm) telescope at x 50. Camera was allowed to autofocus and autoexpose at ISO 200. Picture slightly unsharp-masked in Photoshop.

make a slightly longer exposure (30 seconds rather than 10) and the stars will appear as short streaks, rather than points, because the earth is rotating.

If your camera has long-exposure noise reduction, turn it on. Otherwise, there will be a few bright specks in the image that are not stars, from hot pixels. If long-exposure noise reduction is available, you can go as high as ISO 1600 or 3200 and make a 5-second exposure for crisp star images.

Focusing can be problematic. Autofocus doesn't work on the stars, and it can be hard to see a star in the viewfinder well enough to focus on it. Focusing on a

Figure 4.4. Lunar seas and craters. Nikon D70s with 50-mm f /1.8 lens wide open, handheld at the eyepiece of a 5-inch (12.5-cm) telescope at x 39, autofocused and autoexposed. Image was unsharp-masked with Photoshop.

very distant streetlight is a good starting point. Then you can refine the focus by taking repeated 5-second exposures and viewing them magnified on the LCD screen as you make slight changes.

The picture will benefit considerably from sharpening and contrast adjustment in Photoshop or a similar program. You'll be amazed at what you can photograph; ninth- or tenth-magnitude stars, dozens of star clusters, and numerous nebulae and galaxies are within reach.

This is of course the DSLR equivalent of the method described at length in Chapter 2 of Astrophotographyfor the Amateur (1999). It will record bright comets, meteors, and the aurora borealis. In fact, for photographing the aurora, a camera with a wide-angle lens on a fixed tripod is the ideal instrument.

Figure 4.5. Orion rising over the trees. Canon Digital Rebel (300D) at ISO 400, Canon 18-55-mm zoom lens at 24 mm, f /3.5, 30 seconds. Star images are short streaks because of the earth's motion.

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Figure 4.6. Blitzkrieg astrophotography. With only a couple of minutes to capture Comet SWAN (C/2006 M4) in the Keystone of Hercules, the author set up his Digital Rebel on a fixed tripod and exposed 5 seconds at ISO 800 through a 50-mm lens at f /1.8. JPEG image, brightness and contrast adjusted in Photoshop. Stars down to magnitude 9 are visible.

Figure 4.7. Comet Machholz and the Pleiades, 2005 January 6. Canon Digital Rebel (300D) with old Pentax 135-mm f /2.5 lens using lens mount adapter, piggybacked on an equatorially mounted telescope; no guiding corrections. Single 3-minute exposure at ISO 400, processed with Photoshop.

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