The purpose of this book is to tell you how to photograph the sky with simple techniques and affordable equipment.

Astrophotography is easier today than when I wrote the first edition of this book fifteen years ago. Telescopes are better built, and films have far less reciprocity failure. Many off-the-shelf consumer films are better than the Kodak Spectroscopic emulsions used by astronomers in the past.

Most cameras, however, have become less suitable for astrophotography and harder to use. Many of the newest cameras can't make time exposures without running down their batteries, and the beginning astrophotographer needs more advice about choosing a good camera. This has accordingly been added to Chapter 9.

Meanwhile, digital imaging has come on the scene, and two chapters have been added to cover it. I've had to be careful because digital technology is still changing rapidly. Nonetheless, digital image processing is our most promising new technique, and even if you don't have a computer, you can make digitally enhanced prints at a workstation at the local camera store. With digital technology, I've concentrated on underlying principles rather than specific equipment.

Most photographic filters are dye filters; that is, they are made of colored glass or of colored gelatin coated on glass or plastic. The table lists most of the dye filters you are likely to encounter; the most useful ones are listed in boldface. Regardless of their color, almost all dye filters transmit infrared wavelengths above 750 nm; that's within the response range of CCDs, silicon-cell exposure meters, and infrared films. That is also why it is not safe to view the sun through ordinary photographic filters.

A filter is considered efficient if it blocks the undesired wavelengths completely while transmitting the desired wavelengths without attenuation. Red, orange, and yellow dye filters are more efficient than those of other colors. Blue dye filters are especially inefficient; they don't transmit all the blue light, nor do they block all the light of other wavelengths.

Interference filters are more efficient than dye filters, but also a great deal more expensive. They use multiple layers of very thin coatings to “tune in” specific wavelengths of light. Nebula filters are interference filters; so are the hydrogen-alpha filters used for narrow-band solar observing. These are discussed on pp. 138 and 102 respectively.

Welcome to astrophotography! This book is for people who want to take pictures of the stars and planets, and, perhaps more importantly, who want to understand how astrophotography works. The earlier chapters contain instructions for beginners, and the later chapters are more like a reference book.

My goal is to show you how to do astrophotography at modest cost, with the equipment and materials an amateur can easily obtain and use. I haven't covered everything. I've concentrated on 35-mm cameras and relatively inexpensive telescopes, 20-cm (8-inch) and smaller. Techniques that require unusual skill or expenditure are mentioned only briefly with references to other sources of information.

The challenge of astrophotography

Why photograph the sky? Because of the great natural beauty of celestial objects, because your pictures can have scientific value, and, perhaps most importantly, because you enjoy the technical challenge. Astrophotography will never be a matter of just taking snapshots, and Kodak's old slogan, “You press the button, we do the rest,” certainly doesn't apply. Astrophotographers push the limits of their equipment and materials, and a good astrophotographer has to know optics and film the way a race-car driver knows engines. There are three main technical challenges:

• Most celestial objects require magnification; that's one reason we use telescopes. (Not all objects require magnification; star fields, meteors, and bright comets can be photographed with your camera's normal lens.)

• Many celestial objects are faint, requiring long exposures to accumulate light on the film. In fact, astronomical discoveries have been made this way; the Horsehead Nebula and Barnard's Loop are too faint to see with any telescope, but are not too hard to photograph.

• […]

The following pages are excerpts from film data booklets, reproduced by permission of Eastman Kodak Company. The films covered are:

1. • Kodak Technical Pan Film (black-and-white)

2. • Kodak Professional Ektachrome Film E200 (color slides)

3. • Kodak Professional Ektapress Films (color negatives)

To save space, some information not relevant to astrophotography has been left out. Complete, up-to-date data booklets are available from Kodak and other film manufacturers.

Because products change frequently, you should always use the most current information. These data sheets will remain useful as a basis of comparison for evaluating newer products.

Kodak Technical Pan Film (TP)

From Kodak Publication P-255, June, 1996. Copyright © 1996 Eastman Kodak Company

DESCRIPTION

KODAK Technical Pan Film is Kodak's slowest and finest-grained black-and-white film for pictorial photography (when developed in KODAK TECHNIDOL Liquid Developer). It is a variable-contrast panchromatic film with extended red sensitivity; because of its extended red sensitivity, it yields prints with a gray-tone rendering slightly different from that produced by other panchromatic films. (This is most noticeable in portraits, in which it suppresses blemishes.)

Use this film for pictorial, scientific, technical, and reversal-processing applications. It is an excellent choice for making big enlargements or murals.

APPLICATIONS

You can vary the contrast of KODAK Technical Pan Film by modifying development. The wide range of contrast levels, along with the spectral sensitization and combination of speed and image-structure properties, makes this film unusually versatile and suitable for many applications:

1. • Pictorial photography

2. • Photomicrography

3. • Microphotography (Microfilming)

4. […]

Amateur high-resolution photography of the sun, moon, and planets is a neglected field. I must confess to having neglected it myself, favoring wide-field deep-sky work like so many other amateurs. But high-resolution solar-system photography has several attractions. You can do it in town or even in a large city; you don't have to go elsewhere in search of dark skies. You don't have to wait for the moon to get out of the way; in fact, the moon is one of the targets. Perhaps more importantly, the appearance of the sun and many of the planets is constantly changing, so it's worthwhile to keep photographing the same object; the pictures stand a good chance of having scientific value.

With the advent of digital image enhancement – which often improves planetary pictures dramatically – and the publication of excellent handbooks by Dobbins, Parker, and Capen (1988) and Dragesco (1995), interest in the solar system may be reviving. This chapter will tell you how to get started with this rewarding kind of work.

Film or CCD?

The advent of CCD imaging has made it easier than ever for amateurs to obtain excellent images of the sun, moon, and planets. My first CCD image of Jupiter, taken with an 8-inch telescope, surpassed all my earlier photographs. There are several reasons for this. Unlike a conventional camera, a CCD does not produce any shutter vibration.