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.

The beginnings of this second international colloquium on Astronomy Teaching, eight years after the famous one in Williamstown, came during a meeting of Commission 46 in August 1994, in the Hague. It was then submitted as an IAU Colloquium by the President of Commission 46, John Percy, with the support of the newly born European Association for Astronomy Education.

When I was asked to chair the Scientific Organising Committee, I considered this proposal to be a great honour, that I acknowledge, and also an exciting way to learn more about the new developments in astronomy education that you are performing, so many of you, all around the world.

Then came a hard work! Step by step the programme was built, thanks to the help and suggestions from the SOC members, and I would like to mention more particularly Julieta Fierro, Andy Fraknoi, Barrie Jones, Derek McNally, John Percy.

It was my great pleasure, each day, to read your mails on my computer, or on the fax machine a pleasure mixed with some increasing anxiety, when their number began to grow rapidly! The Internet gives this beautiful possibility to interact so easily with people spread out all over the world – you have just to take account of the time zones, which could be also considered as a good astronomical exercise.

Eight years have elapsed since the first IAU Colloquium (No. 105) on astronomical education “The Teaching of Astronomy”. In that time there have been substantial changes in the world of education – not just astronomical education. On the one hand, there has been erosion of funding, while on the other there has been an unprecedented opening up of access to information: there has been a change from educational experiment towards more regulation of curricula and determination of standards. But, as a reading of this volume will clearly show, there is still a healthy creativity in astronomy education. There is much important new work being done – there are adventurous schemes in public education, there is new detailed research on how our students and pupils may learn and on the portfolio of misconceptions under which they may be labouring when first confronted with astronomical teaching. One of the new features since 1988 is access to the Internet. An overwhelming variety of information is now readily available from the latest Hubble Space Telescope picture to the Web Page of the local astronomy society. But it is also clear that the sheer richness and variety of the Internet offering creates yet another problem – how to organise that information to maximum teaching and learning benefit. The North American continent is once again in a period of curriculum renewal and it is of great interest to see the interaction between that renewal, electronic media and the Internet. Such enterprises are receiving support in particular from the National Science Foundation in the USA. It is encouraging to see that the Internet is being used to support undergraduate projects.

Primary school

School education in Latvia, as in many other countries, is divided into two stages: primary and secondary education. Primary education is compulsory. Every year 30 000 new school children start attending primary school. This is a potential audience that can study astronomy fundamentals. During first grade studies school children learn the basics of natural science which include some elements of astronomy. These lessons are given once a week. At this stage children's interest in the Universe is great; therefore the most active teachers use some out of curriculum activities to give the schoolchildren an idea about the stars, planets and other celestial bodies. The science curriculum itself contains very few elements of astronomy (Karule, 1995). Even more many teachers have problems teaching science at the elementary school, because they are afraid that it is too sophisticated. This situation should be corrected, but at the moment no teacher training in science is planned.

In higher grades of primary school some astronomy elements are taught in different disciplines. In geography there are some topics about the Earth, Seasons and Tides (Klavins, 1992). In physics there are some topics about Eclipses of the Sun and the Moon (Kokare, 1992). And that is all. It leads to the situation that a young person, graduated from primary school, has heard nothing about constellations, Moon phases, comets and many other astronomy questions.

The expected positive changes are the following: new textbooks of the basics of natural science, where more attention is paid to astronomy, are being developed. The textbook for 1st grade has already been published (Vaivode et al., 1995), the others will follow.

Introduction

In recent years much research into conceptual understanding of science has been carried out. Oddly, Astronomy (one of the smallest sciences in terms of pupil numbers) is possibly one of the most widely studied subjects, with numerous papers being produced revealing the intuitive ideas of (usually) young school children. Within these papers it is generally recognised that if students cannot assimilate the fundamental concepts of a subject, then their own initial frameworks are altered accordingly, producing mis-conceptions.

Much of this research into pre/mis-conceptions, alternative frameworks etc, has been concerned with the knowledge of gravity or the shape of the Earth, the Sun and other such bodies. Another area heavily researched is that of phases/eclipses, and how the young children of today perceive these phenomena.

The research presented here takes the findings from earlier papers and extends it by assessing astronomy students at the University of Plymouth. The experiment probed two areas, the phases and eclipses of the moon and Sun and the ability of students to de-centre.

Previous Studies

It has been known for many years now that children usually start to think of the Earth as flat (Vosniadou et al (1989)), with age usually removing or adjusting initial frameworks. This may be demonstrated by assuming we have two children, A and B, which both hold the notion of a flat Earth. From the flat Earth model, child A may ‘leap’ to the concept of a spherical Earth straight away; the child's flat Earth conceptions have been removed and replaced with a model which the child is able to associate with ‘space’ and thus a spherical Earth.