In praise of the DIY Telescope

Light is fascinating. Without visible light, we are blind and yet, paradoxically, its absence helps us to see the stars at their best. Light is both enemy and friend.

Ancient light, recently mapped by the Planck satellite, reveals a visible universe 50 million years older than was previously thought, at 13.82 billion years.

Our spiral neighbour, the Andromeda Galaxy, is light years away but can be seen on a dark night with binoculars, even from an urban location. Sometimes, with the naked eye. A fuzzy patch of starlight, emitting photons that have sped through space at around 1079 million kph (670 million mph) for over 2.54 million years, to eventually reach our retinas. We are truly gazing into the distant past. Time-travelling.

Nearer to home, our Moon has no intrinsic light of its own but reflects that of the Sun (its albedo). As it orbits the Earth every 27.5 days, its lunar phases wax and wane under the Earth’s shadow, from crescent to quarter to Full Moon and back. An easy method of telling if the Moon is waxing or waning is to trace the round curve of its illuminated edge. If the resulting shape forms a letter ‘b’, it is before Full Moon, so waxing. A letter ‘a’ indicates that it is after Full Moon and so on the wane.


Light can also be manipulated: focused and magnified. Telescopes.

From Patrick Moore to Brian Cox, astronomy has evolved spectacularly over the last fifty years. Today, you can easily order yourself a reasonably priced, shiny new ‘go-to’ telescope, online. Just power it up, align to two stars, press a button and you are ready to explore the night sky from your garden. If you’re clever, you can hook the whole set-up to your laptop or PC and visit the Universe from the comfort of your living room.

Of course, you can also have much the same experience through your plasma TV screen, with the added bonus of Professor Cox as your guide and travelling companion. But if you prefer to find things out for yourself rather than be spoon-fed facts, you might have been better off back in the days of black-and-white.

Growing up with Patrick, the only way most people could acquire a telescope of any real size was to build their own. Amateur telescope making (ATM) was in its heyday and the art was carefully honed and passed on from old to young, mainly through amateur astronomy clubs, with assistance from the Jedi masters of the ATM world at that time: Ingalls, Texereau, Thompson and Berry. Armed with their DIY bible of choice, enthusiasts would grind, figure and polish mirrors and put together simple telescope tube assemblies in small workshops up and down the land.

I made one myself. I joined Birmingham Astronomical Society in 1997 after rediscovering my childhood fascination with the night sky. With the invaluable help and advice of Society members, I ground my own mirror and constructed a basic reflecting telescope on a Dobsonian mount that I still use today.

The simplest telescope to build is the traditional Newtonian-type reflector. Housed within a suitable tube or box, a round, concave mirror at one end acts as a primary surface to gather light to a specified focal point and reflect it onto a small, flat, secondary mirror. This secondary mirror is set at an optimal angle to bounce the light up through a focuser and into the eyepiece. The bigger a telescope’s light bucket (primary or objective mirror), the greater the detail and the better the image. Whether you want to focus on the Moon and the planets or on deep-sky objects such as galaxies and nebulae, you can customise your own telescope by fashioning a piece of glass and moulding the mirror to your personal specification.


Like archaeology, astronomy is one of the few sciences to which non-professionals can still make significant contributions. Discovering a previously unknown asteroid will enrich the soul of the enthusiastic astronomer as much as unearthing a Saxon hoard may profit the pocket of the keen weekend digger. Dedicated amateur stargazers have identified countless asteroids, comets and variable stars over the years with only the most basic equipment. Nowadays, technology has made it even easier.

Space exploration need not be confined to NASA and its billion-dollar budget. With a telescope, whether homemade or commercial, we can all travel the solar system and beyond without ever leaving the Earth. You just need imagination, a keen sense of curiosity and an unending capacity for wonder.

And a dark sky, of course. To see the light.

The late Carl Sagan defined science as a candle in the dark. He might have been describing a telescope.

By Gill Pilfold