How to Buy a Telescope
Credit: Eugen Naiman

How to Buy a Telescope

07/12/2016Written by Tamela Maciel

A guide to telescopes and answers to the most frequently asked questions.

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Buying a first telescope all depends on what you want to see and how you plan to use the telescope.

This guide answers the questions that we are frequently asked at the National Space Centre to help you find the perfect telescope.

I’m brand new to stargazing. How do I get started?

I’m brand new to stargazing. How do I get started?
Credit: Stellarium

One of the best ways to start exploring the night sky doesn’t require any special equipment. Grab a friend on a clear night and head for the hills! Find a spot away from city lights, tall buildings, and trees and just look up. Enjoy seeing all of the stars that aren’t normally visible in the glare of cities.

To start finding constellations, bring along a current star chart (we like the free printable charts from Skymaps.com) or download a stargazing app on your phone. Bring a red light with you to avoid ruining your night vision.

Also look out for stargazing events near you. Most local astronomical societies will organise a few of these a year and they are a great way to learn more about the night sky and a chance to look through different telescopes.

Tell me the basics

Tell me the basics
Credit: Grand Canyon National Park

It’s easy to be overwhelmed by the specs and options when buying a first telescope.

The key spec for any telescope is its aperture, or the diameter of its lens or mirror. The bigger the better because a bigger aperture can collect more light and distant objects appear brighter. But this comes at a price, and bigger telescopes are also much less portable. Consider whether you want to be able to load your telescope into the back of your car for stargazing field trips before splashing out on that 10-inch aperture telescope.

To determine what type of stargazing a telescope is best for, look at its f-ratio. The f-ratio is the telescope’s focal length divided by its aperture. For a telescope with a 900-mm focal length and a 70-mm aperture, this gives an f-ratio of 12.9 or f/12.9. As a general rule, the smaller the f/number, the lower the magnification, the wider the field, and the brighter the image.

Small f-ratios of f/4 to f/5 are best for wide-field observing and deep space objects such as galaxies. Large f-ratios of f/11 to f/15 are better for narrow-field, high power views of the Moon, planets, or binary stars. Medium f-ratios f/6 to f/10 work well for either.

What are the different types?

What are the different types?
Credit: Sky & Telescope, Gregg Dinderman

Beyond aperture and f-ratio options, telescopes come in three basic types: refractors, reflectors, and compound.

Refractors are common starter telescopes and easily recognisable. The user looks through an eyepiece at the end of the telescope, along a series of glass lenses, to see a magnified night sky object. Refractors are good for seeing craters on the Moon, bright planets, or even daytime landscapes and wildlife. They’re easily portable and simple to aim. But bigger, more powerful refractors become expensive and inconvenient to look through because the eyepiece is low to the ground.

Reflectors use mirrors instead of lenses to reflect instead of bend the incoming light. This means that the eyepiece can be placed in a more convenient location on the side of the telescope. As large mirrors are cheaper to manufacture than large lenses, reflectors are better value as the size goes up. Reflectors are popular choices for people looking to see deeper into the sky (Saturn’s rings, Jupiter’s moons, nebulae, and nearby galaxies). Reflectors are also known as Newtonian telescopes because, you guessed it, Sir Isaac Newton invented them. His model from 1668 is the earliest known type of a reflecting telescope.

A third type of telescope is a combination of a refractor and a reflector. Known as a compound or catadioptric telescope, it uses both lenses and mirrors to make a powerful telescope with a short tube length. Like a refractor, the eyepiece is still at the end of the telescope, but its shorter length means that it’s not as inconvenient to look through. Compound telescopes are more expensive than refractors or reflectors, but far more portable than reflectors for a similar magnifying power.

You’ll find countless options within these types. The key thing is to go with a reputable astronomy brand. Excellent telescope brands include Orion, Celestron, Bresser, Meade, and Sky-Watcher.

Does the telescope mount matter?

Does the telescope mount matter?
Credit: Ryan Wick
Does the telescope mount matter?
Credit: Steve Richards, Sky At Night

A telescope mount is the base of the telescope. It supports the telescope off the ground and allows it to point in different directions and at different angles.

The mount is arguably just as important as the telescope itself if you want to get a clear, sharp image. A cheap tripod will wobble at the slightest touch and any image in the telescope will be shaky. A heftier mount will keep the telescope still so that the image is clear, but this can mean that your telescope is much less portable. It’s about finding the right balance for your needs and budget.

Steer clear of flimsy, high street tripods in favour of better quality mounts from dedicated telescope brands and you should be alright.

You may see the terms alt-az and equatorial bandied about when looking at mounts. These refer to how the telescope can be adjusted to point at a particular part of the sky. Alt-az (short for altitude-azimuth) is the simplest system. The telescope can swing left-right and up-down on the mount, just like a camera tripod. An equatorial mount works in a similar way, but it’s tilted so that the telescope naturally traces along the paths of stars in the sky. This makes it possible to easily follow stars and other deep-sky objects over time.

Many amateur astronomers are partial to the good value and sturdiness of a Dobsonian mount. This is an alt-az mount that supports larger telescopes. Its design is so simple that it can even be made at home.

Having covered the telescope basics, here are a few suggestions depending on what you’re looking for.

I want to see star constellations and meteor showers

I want to see star constellations and meteor showers

No telescope needed! The best way to begin stargazing is to get familiar with the winter and summer constellations. This is like learning a new map. You’ll find it much easier navigate by telescope once you know how to locate a few constellations by eye.

Meteor showers are best viewed with the naked eye. These bright streaks of glowing dust and rock cover a huge area of sky and are gone in an instant, so no specialist equipment is needed, just a bit of patience.

To find out about upcoming meteor showers and how to view them, download our National Space Centre Meteor Shower Guide.

I want to see craters on the Moon and the planets

I want to see craters on the Moon and the planets

To explore the detailed surface of the Moon, as well as the planets, look for a narrow-field telescope with a large f-ratio (f/11 to f/15).

This will allow you to see Jupiter’s four Galilean moons, the stunning rings of Saturn, and even the multi-coloured bands of Jupiter’s clouds. A large f-ratio is also great for spying double stars and exploring the craters of the Moon. Orion’s SkyQuest XT4.5 Classic* is a good example of its type.

For wider views of the Moon, as well as nearby galaxies and star clusters, grab a good pair of 10×50 binoculars. These will magnify objects by 10 times, yet keep a wide field of view to see large, bright objects. Good brands include Celestron, Helios, Opticron, Revolution, and Strathspey.

See this Binocular Sky article for more information and recommended best buys.

I want to see nebulae and galaxies

I want to see nebulae and galaxies
Credit: Joel Tonyan

For more exotic objects (nearby nebulae and galaxies) a good introductory all-rounder telescope is the Orion SpaceProbe 3*. You can see both planets and galaxies without breaking the bank.

If you’re interested in a bit more deep-space detail, then you’ll probably want to look at a bigger telescope.

For best value, go for a larger reflector telescope (6-inch or above) on a sturdy Dobsonian mount. The Orion SkyQuest XT8 Classic* is consistently rated for its clarity and power, but be sure your passion for stargazing won’t fade before investing in this top-end telescope.

I want to buy a first telescope for a child

I want to buy a first telescope for a child
Credit: Orion

For a child’s first telescope, look for something that is ultra-simple to set up. A good option is a telescope that can sit on a table top, such as the Celestron FirstScope or Orion Funscope Astro Dazzle*.

These reflector telescopes have decent power, a simple alt-az mount, and the ease of a table-top setup. They also come with helpful guides to night sky objects.

I want something that’s easy to move around

I want something that’s easy to move around
Credit: Gary Seronik

For portable stargazing, consider a good pair of binoculars rather than a telescope. Some binoculars can rival small refractor telescopes in terms of magnification, and are much easier to set up.

But if you really want magnifying power and portability, then you may need to invest in a compound telescope such as a Schmidt-Cassegrain or Maksutov-Cassegrain. These telescopes have the maximum magnification for the smallest body size, and can easily fit in the boot of a car.

I want to take pictures with my telescope

I want to take pictures with my telescope
Credit: Joel Tonyan

To do some astrophotography you’ll need an adaptor to mount your digital camera or phone against the eye piece. With a DSLR camera, you can remove the camera lens altogether and use the telescope itself as a lens, mounted with an adaptor ring.

For faint, deep sky objects, you’ll need a long exposure time to collect enough light. In this case, a telescope with a drive motor that tracks the object across the sky as the Earth rotates is needed, as well as a very sturdy, steady equatorial mount that doesn’t wobble.

To find out other astrophotography tips, connect with your local astronomical society.

Where can I find out more?

Where can I find out more?
Credit: James Coleman, LAS

Attend a meeting or stargazing party with your local astronomical society. These friendly groups have a huge depth of expertise on telescopes and astrophotography, and can be an excellent way to get tips and ideas for stargazing.

If you’re based in the East Midlands, the Leicester Astronomical Society meets every other Tuesday evening at the National Space Centre.

Clear skies and happy stargazing!

*Please note that these suggestions are based our opinions as professionals. We are not being paid to endorse or advertise these products.