A Beginner's Guide to Choosing Your First Telescope in the UK

Most first telescopes are bought twice. The first is a department-store box with a picture of Saturn on the front and a magnification figure that turns out to be wishful thinking. The second is bought a year later, after a few evenings spent fighting a wobbly tripod. A little knowledge up front saves both purchases, and it takes about ten minutes to learn.

Aperture first, magnification later

Aperture is the diameter of the main lens or mirror, usually given in millimetres. It is the number that decides everything else: how much light the telescope collects, how faint an object you can see, and how much detail you can pull out of the Moon and planets. Magnification is just a consequence of which eyepiece you slot in, and it can always be changed later.

Ignore packaging that shouts about 500x or 600x. A rough and genuinely useful guide is that the highest magnification a telescope handles well is about twice its aperture in millimetres, and only on a steady night. A 130 mm scope will rarely reward you past roughly 260x; a 70 mm refractor tops out near 140x. Anything beyond that is an empty, blurry image. A well-made 130 mm or 150 mm instrument will show you Jupiter's cloud belts, Saturn's rings and the craters of the Moon with real clarity. A 60 mm scope promising 525x will show you a smudge.

Mounts: alt-az, Dobsonian and equatorial

The mount matters as much as the optics. A brilliant telescope on a shaking tripod is worse than a modest telescope on a solid one.

• Alt-azimuth (alt-az): moves up and down, left and right. Intuitive, light, and the sensible starting point for most people.
• Dobsonian: a Newtonian reflector on a simple wooden rocker box, which is itself a form of alt-az. You get the most aperture for your money, but the tube is large and the mount does not track objects as the Earth turns.
• Equatorial: tilted so one axis matches the Earth's rotation. Once aligned roughly towards Polaris, a single slow-motion knob keeps an object centred. Excellent for long observing sessions and astrophotography, but heavier, more fiddly to set up, and often awkward to carry outside.
• Computerised (GoTo): motorised mounts that find objects for you after a short alignment routine. Genuinely helpful in light-polluted skies, but they need power, patience and a little reading before the first session.

For a first scope, an alt-az or a Dobsonian is usually the least frustrating choice.

Portability and the British weather

Clear evenings here arrive in short, unpredictable windows. The telescope you use is the one that is quick to carry outside, not the one with the biggest mirror. Before buying, measure your storage space, count the stairs, and think honestly about whether you will move it alone in the dark.

A 200 mm Dobsonian is roughly a metre of tube and often needs two trips to the garden. That is fine if you have a back door and a shed. It is miserable from a third-floor flat with a shared balcony. Tabletop Dobsonians and small refractors fit on a windowsill or a sturdy garden table and get used far more often.

Two practical points. Newtonian reflectors may need collimation — aligning the mirrors — occasionally, which is straightforward with a Cheshire eyepiece or a laser collimator and a little practice. And allow a larger scope twenty to thirty minutes outside to cool to the ambient temperature; until then, high-power views look soft and disappointing.

What light pollution takes, and what it leaves

Most of us observe from towns and suburbs. Light pollution washes out faint, spread-out objects: nebulae, galaxies, and the Milky Way itself. It does very little to the Moon, the planets, double stars, and bright clusters, which is why a first telescope in a city still has plenty to show you.

• Set up in the darkest corner of the garden and block direct light from streetlamps or a neighbour's security light with a screen or a hedge.
• Give your eyes twenty minutes to adapt, and use a red torch rather than a phone screen when you need to check a chart.
• Observe an object when it is highest in the sky, where you are looking through the least atmosphere.
• For galaxies and nebulae, a trip to a darker site will improve the view more than a bigger telescope will.

Light pollution filters can help slightly with certain nebulae, but they will not turn a city street into a dark-sky site.

What to look at first

The Moon is the best starting target: dramatic, easy to find and different every night along the terminator, the line between light and shadow. Then Jupiter with its four bright moons, Saturn's rings, the phases of Venus, the Orion Nebula, the Pleiades, and double stars such as Mizar or Albireo. Manage your expectations kindly: planets appear small but detailed, and most nebulae look grey rather than colourful through an eyepiece. That is normal, and it is still wonderful.

Buying sensibly

Avoid any telescope that advertises extreme magnification, plastic optics or a tripod that flexes when you touch it. Those boxes exist to be bought once and abandoned. A 130 mm tabletop Dobsonian, a 150 mm or 200 mm Dobsonian, or a small refractor on a decent alt-az mount are the reliable routes in.

Also worth knowing: 10x50 binoculars are a legitimate first instrument and will show you the Moon's craters, Jupiter's moons and dozens of star clusters.

Buying second-hand is a good way to get more aperture for your money. Check mirrors and lenses for scratches or coating damage, feel whether the mount moves smoothly without play, and confirm that eyepieces and the finder are included. Astronomy clubs and local societies often run public observing evenings where you can look through member scopes and ask questions before spending anything. That single evening is worth more than weeks of reading.

Whatever is in the box, learn to align the finder in daylight, and start with the lowest magnification eyepiece you have before working upwards. Two eyepieces of reasonable quality beat five poor ones, and a moon filter is one of the few accessories genuinely worth adding early.

Your first night: a short routine

1. Set up in daylight if you can, and point the finder at a distant chimney or pylon while lining up the main scope on the same object.
2. Carry everything outside before dusk and let the telescope cool.
3. Start with the Moon or a bright planet at low power, and focus slowly.
4. Only then increase magnification, and back off if the image turns soft.
5. Keep a notebook, or a note on your phone, of what you saw and when.
6. Expect the first session to be fiddly and the second to be easier.

The best first telescope is not the largest one you can afford. It is the one that lives close enough to the back door that you will actually carry it out when the clouds finally part.

Photo: anselmo7511 / Pixabay