Around 1999 and 2000, when amateur astronomers adopted computerized telescope technology en masse, three telescopes led the revolution. They were the Meade LX200 (on the market since 1992), the Meade ETX-90 EC Autostar (introduced in 1999), and the Celestron NexStar 5 (2000).

The following chapters describe these telescopes in some detail. By now, none of them is still the manufacturer's latest and greatest. Technology is progressing so fast that new models appear almost every month.

But the older telescopes will still work as well as they ever did, and tens of thousands of them will remain in use for many years. The information in the next three chapters will help those who still use classic computerized telescopes, or are thinking of buying them, or simply want to know what they are like.

Light without form

The price we pay for city life is blank urban night skies, rendered almost starless by our addiction to light. Electric light is, without doubt, a ‘good thing’. But, like all good things, you can have too much of it. Many of our cities are so brightly lit that our eyes are perpetually dazzled, and we are unable to see any but the very brightest stars and planets.

Together with its companion volume, How to Use a Computerized Telescope, this book is a guide for a new generation of amateur astronomers. The two books began as a single project, originally a list of interesting objects that I put together for my own use at the telescope. Soon I added a concise summary of the Meade LX200 operating manual. Simon Mitton of Cambridge University Press saw my notes and encouraged me to turn them into a book. As the project grew, it became two books instead of one – a book about telescopes and a book about the sky. This volume is the latter.

While I was writing the two books, Scott Roberts of Meade Instruments lent me equipment to try out. The technical support departments at Meade, Celestron, Software Bisque, and Starry Night Software answered technical questions. Daniel Bisque supplied software for testing. Howard Lester, Dennis Persyk, Lenny Abbey, Rich Jakiel, T. Wesley Erickson, Robert Leyland, R. A. Greiner, Richard Seymour, Ralph Pass, Phil Chambers, Ells Dutton, Michael Forsyth, and John Barnes critiqued drafts of parts of the text. Tom Sanford let me try out his Meade LX90 at length. Earlier, Jim Dillard first got me interested in computer-aided astronomy by buying my old Meade LX3 from me and outfitting it with digital setting circles. There are probably others whose names I've forgotten to list, and I beg their indulgence.

Back in the 1850s, T. W. Webb noticed that amateur astronomy had become competitive – his contemporaries were trying to outdo each other by building larger and larger reflectors. He decided to break out of this trend and write a book for owners of 3-inch refractors and the like. His book, Celestial Objects for Common Telescopes, has become a classic and is still available.

In a similar spirit, I want to break away from the present-day tendency to equate deep-sky observing with star-hopping to the faintest possible nebulae and galaxies, which are visible only under extremely dark skies. There's more to the stellar universe than just “faint fuzzies.”

The objects in this list are visible with an 8-inch (20-cm) telescope under suburban skies with a naked-eye magnitude limit of 5. Most of them are fine sights even with considerably smaller telescopes under worse conditions. Many of them are stars (variable, double, multiple, or unusually colored) or bright star clusters.

This list is based on my own observations. It is organized by zones of right ascension, and within each zone, in sequence from north to south. Chapter titles such as “The January–February sky” refer to the time of year when the objects are highest at 10 or 11 p.m. local time. Many of the objects, especially the more northerly ones, can be viewed for much longer than just the specified two-month period. Those in the extreme south, however, are in the sky only briefly.

Since this book is intended to encourage you to use your eyes, unaided by a telescope, I should begin by saying a few words about the eye. Many people assume that the eye is like a camera, and that therefore we must see whatever is before our eyes. But, to see, you must look. Seeing is a conscious act and, unless you look actively, and have some idea of what you are looking for, you probably won't see many of the things mentioned in the subsequent pages.

Computerized telescopes are revolutionizing amateur astronomy. Even the least expensive entry-level telescopes are now available with computer-controlled motors to find and track objects in the sky. No longer do you have to search for NGC 1999 or Neptune by carefully comparing the view with a star map – you just tell the telescope what to point at, and it does it.

Do computer controls take all the fun out of astronomy? No more than paved highways take the fun out of the Arizona desert. Professional astronomers have used setting circles to find objects since the time of Tycho Brahe and have always tried to make them as accurate as possible. Amateurs have long had setting circles, but they weren't very accurate. Now, with the advent of computers, professional-level accuracy is within the reach of the amateur, and the computer actually controls the telescope rather than just telling you where it's pointed.

After 30 years of finding celestial objects the old way, I bought my first computerized telescope in 2000 and immediately found myself doing a new kind of amateur astronomy. Suddenly I was spending my time looking at objects instead of for them. No longer preoccupied with “star-hopping”, I could spare the time and attention to study the celestial objects themselves.

In fact I realized for the first time that, for all those years, my observing program had been skewed by the fact that some objects are easier to find than others.

This chapter gives quick solutions to a number of common problems that are likely to puzzle a new telescope owner. This list is far from complete. For more information, see your instruction book, as well as Chapters 10–12 and the websites mentioned there.

Electrical and computer problems

Telescope is electrically dead

Check all fuses. On the LX200, there is a fuse inside the connector panel as well as in the power cable.

Check keypad and declination cables too. If deprived of any of its necessary connections, the computer will not initialize normally and the telescope may seem to be electrically dead.

Check for a coaxial power connector that is the wrong size. The diameter of the central pin is smaller on Celestron than on Meade telescopes. The Meade connector fits Celestron telescopes but gives a loose connection.

Computer hangs or resets at random moments

This is often caused by a loose connection somewhere in the power system; inadequate battery voltage; or electrical noise on the power line, such as poor filtering of an AC-operated power supply.

If using internal batteries, check the battery contacts and try using an external power supply. Rechargeable lead-acid batteries are the gold standard for power supplies; they produce very clean, well regulated DC.

Make sure coaxial DC connectors are the right type and are firmly plugged in. On the NexStar 5 and some others, the central pin of the socket consists of two tines that you can spread apart with a screwdriver to get a better connection.

Small objects in the Solar System

A century ago, astronomers' picture of the Solar System was neat and clear. There were eight planets and an asteroid belt, a set of small, rocky bodies between the orbits of Mars and Jupiter, presumably the remains of a planet that had exploded or never formed.

By 1950 the picture was a bit less tidy. One planet, Pluto, was abnormally small and had an odd orbit. A few asteroids had been discovered with orbits outside the asteroid belt.

Today the situation is even less neat, and we are having to rethink old categories. Though the belt between Mars and Jupiter is predominant, there are asteroids all over the Solar System, including a second belt, the Kuiper (KHOY-per) Belt, outside the orbit of Neptune.

There is no longer a clear distinction between asteroids and comets; the asteroid 2060 Chiron has played both roles. It now appears that a comet is merely an icy asteroid from the outer Solar System that has been deflected close enough to the Sun to vaporize the ice.

The distinction between asteroids and planets is also becoming blurred; some scientists want to reclassify Pluto as the largest Kuiper-belt asteroid. Meanwhile, some planetary satellites, such as Mars' potato-shaped companions Phobos and Deimos, are physically indistinguishable from asteroids.

Overview

All stars are variable – it's just that some of them have not varied appreciably during human history. Every star changes brightness as it ages, and many stars pulsate – that is, they get brighter and dimmer in a regular cycle.

Besides being interesting to watch, variable stars provide opportunities for amateurs to contribute to scientific knowledge. Much of the year-by-year monitoring of variable stars is done by amateurs, and amateurs discover many novae and supernovae. A large telescope is not required; some of the most productive observers use small, wide-field instruments or even binoculars.

Amateur variable-star work is coordinated by the B.A.A. (p. 30) and the American Association of Variable Star Observers (AAVSO, 25 Birch St., Cambridge, MA 02138, U.S.A., http://www.aavso.org). The AAVSO maintains a web site with current information on thousands of stars and issues bulletins about unexpected phenomena.

Besides AAVSO and B.A.A. training materials, two very good guides to variable-star observing are the book Observing Variable Stars, by David H. Levy (Cambridge University Press, 1998), and the chapter on variable stars by M. Dumont and J. Gunther in Patrick Martinez' The Observer's Guide to Astronomy, vol. 2, pp. 775–846. Levy's book is designed for beginners and casual skygazers; Dumont and Gunther's treatment of the subject is more technical.

Contemporary science has uncovered the relation between time and physical processes, making it possible to ‘grope’ for the first links of the time chain in the past and to project its properties to the distant future.

But what does modern science say about why time flows at all, and why only from the past to the future? I should immediately say that experts still lack an exhaustive, clear and generally accepted answer to this question. Nevertheless, a great deal has been achieved in this field, too, and we will have a quick look at some fragments of the achievement of the science of time.

In the post-Newtonian era, physicists have always emphasized a surprising property of the laws of nature: they do not in any way single out the direction of time flow from the past to the future.

We easily recognize this fact by looking at the simplest problems in mechanics. For example, let a ball roll along a surface, hit a wall at a certain angle, rebound and continue rolling. Now we can, in our minds, reverse the direction of time and imagine the ball rolling in the opposite direction, going through all the points of its trajectory in the opposite order. It is as if we had filmed the experiment and then projected the film beginning with the last frame. All laws of mechanics describe the motion of the ball equally well both in the forward and the reversed directions of time flow.

Here unfolds the story of the momentous achievements of science in the 20th century. I would say that the most impressive discovery was made at the very beginning of the century by Albert Einstein when he created relativity theory. He showed that there does not exist any ‘absolute time’, no unified unchangeable river of time which impartially carries all events occurring in the Universe.

Academician A. Alexandrov of the Academy of Sciences of the USSR wrote: ‘Einstein's greatest discovery which became the cornerstone of relativity theory and a turning point in the general physical and philosophical interpretation of space and time was the revelation that nature knows no absolute time.’

Evidently, time behaves as a river with constant, unchangeable flowrate only in the habitual conditions of relatively slow motions and not very high interaction energies. Its properties are very different under very unconventional conditions! We will discuss this later in great detail.

The discovery of the relative nature of time is contained in relativity theory that Einstein created in 1905. An enormous number of books have been written about Einstein, definitely more than about any other physicist. Several factors explain this. I will quote the opinions of several well–known scientists who knew Einstein personally, and also Einstein himself; these sources may help, to some extent, to reconstruct the image of this personality and to understand the causes of his immense popularity.

Which of us was not immersed in our youth in Herbert Wells' famous short novel The Time Machine? The protagonist of this story uses a device that can travel in time to visit a very remote future of the Earth. Wells also imparted to this device the property of reverse motion into the past.

A large number of books have been written which fantasized about the possibility of freely visiting the past and the future. In all likelihood, their authors were never in doubt that their inventions belonged to pure imagination and treated this as nothing more than a literary stratagem.

The entire experience of mankind and scientific knowledge have made inevitable the conclusion that travel in time is impossible. Space is where motion is allowed. Say, travel on the Earth is possible in different directions and one can also return to the starting point. On the contrary, we are seemingly unable to choose the direction of motion in time, we are bound to ‘float’ passively in this flow. It was assumed that here lies the dramatic difference between time and space.

Einstein's discovery of the surprising properties of time in 1905 demonstrated the fallacy of the view that we are ‘captives’ of the river of time and thus cannot ‘steer’ on it; it was seen as a fruit of not knowing, as a consequence of the limited possibilities that mankind had during its preceding history. But does this mean that we are free to roam in time?

I began preparations to publish this book in English at the end of 1991; for a number of reasons, this stage stretched to several years. An oriental adage says: ‘Hours tick away, days run away but years fly away.’ These words are a reflection of our subjective perception of time intervals in the past, of what we remember of them. For most people, the feeling of the flight of time is considerably intensified when one turns in one's mind's eye to larger and larger blocks of time which one has lived through. I distinctly feel now that it was virtually yesterday that I was writing this book, even though several years separate me from those days and so much has happened and so much has changed. In that period, I began working in a new place, as astrophysics professor of Copenhagen University. My native country, the former USSR, the former enormous empire, broke into pieces and is trying, in untold hardship for its peoples, to claw its way out of the frightening historical abyss into which it had been plunged. Even though I continue to head the Department of Theoretical Astrophysics of the Petr Lebedev Physics Institute in Moscow, my settled life beyond the borders of my native land, in a very different world, has definitely changed my perception of life, although to a considerably lesser degree than I could have predicted. It involves my attitude to this book as well.

Despite all this, in spite of all the progress, the nature of time remains to a large extent a mystery for us. Regardless of the millennia counted by the history of science, we are only at the very beginning of the way to comprehend the essential meaning of time flow.

Our knowledge about this ‘grand river’ was gleaned very slowly. The science of the ancient Greeks defined the concept of time as an independent category, as a universal property inherent in all objects and phenomena of the material world. It also established that time does not move in circles, that it is not cyclic, that it moves inexorably from the past to the future.

The laws of classical physics, which found their exhaustive expression in Newton's work, assigned to time the role of empty duration, without beginning or end, flowing eternally at a constant rate, regardless of what events take place in the world.

The revolution in physics that began a century ago, and the subsequent relentless progress in this science produced, numerous overwhelming discoveries. We now know that the rate of flow of the river of time can indeed be influenced. In principle, a ‘flight’ can be made to the very distant future, and, who knows, one may be able to move ‘upstream’ on the ‘time river’, that is, into the past; technically, of course, both sorts of time travel remain unfeasible at present.