A beginner's guide to Telescopes
- 6th Dec 2023
- Author: Lucy Spencer
Telescopes are amazing. They’ve been used for great discoveries such as the rings of Saturn in 1655, and the distant planet Uranus in 1781. The universe is full of wonders we can’t observe with the naked eye, and anyone can use telescopes to reveal them! Seeing pictures of celestial objects is great, but there’s nothing like seeing the real thing with your own eyes. Read on to discover more about telescopes and what to look for with them.
What to look for in the night sky
Winter stargazing
From the perspective of the Northern Hemisphere, where the UK is located, it’s great to stargaze during the winter as it gets dark early.
The most prominent constellation you’ll be able to spot in winter is Orion (the Hunter) – recognisable by his ‘belt’, which consists of three bright stars. Within this constellation, you’ll be able to see the Orion Nebula with binoculars or a telescope and even with the naked eye as a fuzzy patch. This is located on Orion’s Sword, just below the Belt.
Another winter constellation is Taurus, one of Zodiac constellations. In Greek mythology, Taurus represents a bull.
The Pleiades, an open cluster of stars also known as the Seven Sisters, is visible in winter above Taurus. Follow Orion's Belt up the sky, passing the bright star Aldebaran in Taurus, until you find the star cluster. You can actually see Pleiades with the naked eye, too. But you can see more stars with a telescope or binoculars.
One of my favourite deep sky objects to view through my binoculars and telescope is the Andromeda Galaxy which is in the night sky in both summer and winter. This galaxy is the nearest spiral galaxy to us and is home to one trillion stars! While we can only really see the bright core of the galaxy with amateur telescopes, if we could see the entire faint disk of the Andromeda galaxy, it would appear six times the width of the Moon in the sky!
Summer Stargazing
Of course, if you’re stargazing in the summer months, you’ll have to stay up later in order for it to get dark. But at least it’s a lot warmer than winter! The best summer constellations to look out for in the UK include Hercules, Sagittarius (one of the Zodiac constellations) and Cygnus the Swan. If you find a dark enough area, you’ll be able to see Cygnus swimming along the faint disk of the Milky Way with the naked eye.
If you have a small telescope or even a pair of binoculars, you will be able to see Messier 13, the Great Globular Cluster, within the constellation Hercules. This huge collection of several hundred thousand stars is often described by astronomers as the most magnificent globular cluster that can be seen in the northern hemisphere.
Observing Planets
Five of the planets in our solar system can actually be viewed by the naked eye - Mercury, Venus, Mars, Saturn and Jupiter. You’ll need a telescope for the other two – Uranus and Neptune. With a telescope or binoculars, you’ll be able to view the planets in much more exciting detail.
Telescopes: An Overview
Telescopes use lenses, mirrors, or a combination of both to gather and focus light. The two main types are refractors, and reflectors.
Refractor
These are lensed telescopes. They use glass lenses to bend or refract light. They’re usually quite lightweight and compact, which makes them more portable, and the images they produce are sharp and detailed, due to the use of the lenses. However, because larger lenses are expensive, their apertures are smaller and more focused – giving a less expansive view of the night sky. You might prefer a refractor telescope when observing planets and the Moon, for example.
Reflector
Reflecting telescopes are more efficient at gathering light due to the use of mirrors instead of lenses. This type of telescope gives a clearer image and wider field of view compared to a refractor telescopes, and they typically have larger apertures. Reflectors are therefore better for viewing faint deep-sky objects like galaxies, star clusters and nebulae. One of their problems, however, is that they are heavier and bulkier than their refracting counterparts.
Catadioptric
Telescopes that use a combination of lenses and mirrors are known as catadioptric telescopes. Making use of both optical systems can make manufacturing easier and can boost performance. They can provide stargazers with wide fields of view, low distortion, and high magnification but are generally more expensive.
Choosing the right telescope
Consider the following factors when selecting a telescope:
Aperture: For deep-sky observations such as galaxies and nebulae, larger apertures (6 inches or more) are preferable. Smaller apertures are better for observing the moon or the planets. The larger the aperture or size of the primary mirror or lens, the more light it can gather and the fainter an object you can see.
Focal length: this determines the magnification and field of view. Longer focal lengths provide higher magnifications but narrower views, while shorter focal lengths offer wider fields of view. While viewing something like the Moon you may want lower magnification so you can see it's entire disk with a background too. For a deep sky object you'd likely want higher magnification so it expands to fill more of your field of view rather than being a small spec of light in a large backdrop.
Mount: two primary types are alt-azimuth (up-down, left-right movement) and equatorial (aligns with Earth’s rotation for easier tracking). A stable mount is crucial for steady observations. Equatorial mounts are good if you want to easily track an object throughout the night as the Earth spins, but require a bit more competency to setup.
Additional features: some telescopes come with accessories such as eyepieces, finderscopes and filters, enhancing your observing experience.
How to use a telescope
Setting up a telescope of course varies from model to model, but an example might be:
- Familiarize yourself: Read the instruction manual thoroughly to understand your the parts of your telescope, assembly, operation, and maintenance.
- Location: find a dark observing site away from city lights for optimal viewing conditions.
- Setup: choose a stable flat surface to assemble your telescope. Attach the telescope to the mount and fix in place the finder scope and eyepiece so that all the pieces are on before going on to the next step.
- Calibrate: balance the optics before use and use the finder scope to align your view through the eyepiece of the telescope. (The finder scope has a wide field of view and low magnification so you can easily find a target and then looking through the telescope you can adjust and focus your view to view at higher magnifications).
- Target objects: start with easy -to-spot celestial objects like the Moon, planets like Jupiter, Saturn and Mars, before moving on to fainter deep sky objects. Use an app or star chart to help find your way across the night sky.
- Patience and practice: experiment with your telescope using different eyepieces and observe regularly to improve your skills.
Good luck!
Binoculars
It's not all about telescopes – binoculars are a great tool to observe various deep sky objects, such as open star clusters like the Pleiades, nebulae like the Orion Nebula (it will appear as a fuzzy patch of light), and the Andromeda Galaxy (which will appear as a faint, disk-shaped smudge). And of course, they’re far more portable and don’t require a telescope’s setup time.
The size of binoculars suitable for astronomy typically range from 7x50 to 20x80. But what do those numbers actually mean?
The first number is the magnification (such as 7x, 10x, 15x). This is how much larger the object will appear to be compared to the naked eye. 7x to 15x show a wider field of view, which makes it easier to locate and observe celestial objects – making this better for beginner astronomers.
The second number is the objective lens diameter (such as 50mm, 80mm). This is the diameter of the front larger lens’. The larger the lens, the more light it gathers – allowing you to observe fainter deep sky objects.
A good compromise for both these numbers would be binoculars in the range of 10x50 or 15x70. This lets enough light through, and a good magnification to view fainter celestial objects.
However, the larger the binoculars, the heavier they are! This becomes a problem when you are trying to observe a celestial object as it is hard to keep your hands steady. This is where a tripod could come in handy to stabilize the binoculars and allow for steady viewing.
Telescopes vs Binoculars
Binoculars, while generally not as powerful as telescopes, are great for beginners. They are easy to use, they don’t need to be set up and have a wide field of view to make it easier to find celestial objects. Binoculars are also more portable than telescopes, so you can easily carry them around and quickly get them out for stargazing.
Telescopes allow you to observe celestial objects in greater detail. They generally have higher magnifications, allowing for close-up views of planets and deep sky objects. For example, you will be able to see Saturn’s rings in more detail - as telescopes have larger aperture so will be able to gather more light. Telescopes can also allow for multiple eyepieces, to change the magnification.
In summary, if you are interested in observing details on planets and close up views of deep sky objects such as the Andromeda Galaxy, a telescope may be for you (refractors are better for observing planets and the Moon, reflectors are better for observing deep sky objects).
However, if you are looking for a more accessible and easy way to observe the night sky, while still being able to see deep sky objects and some planetary detail, binoculars may be a better choice.
Sometimes building familiarity with the night sky using binoculars to get used to stargazing, can make the process of getting and using a telescope, when you eventually do, a more pleasant experience!
Full references / credits:
(Banner image) Telescope. Credit: Ryan Wick CC BY 2.0 DEED (https://www.flickr.com/photos/ryanwick/3461850112/)
(1a) Screenshot of Stellarium showing the winter night sky. Credit: Stellarium
(1b) Screenshot of Stellarium showing the summer night sky. Credit: Stellarium
(1c) A planetary line-up. Credit: Stellarium
(2) The first reflecting telescope built by Isaac Newton in 1668. Credit: public domain
(3) A refractor telescope. Credit: Mark Mathosian CC BY-NC-SA 4.0 DEED (https://www.flickr.com/photos/markgregory/8093678175)
(4) Setting up a telescope. Credit: Tobias Lindman CC BY 4.0 DEED (https://www.flickr.com/photos/cowb0y2000/7558375412)
(5) Binoculars. Credit: doraemon CC BY-NC-SA 4.0 DEED (https://www.flickr.com/photos/doraemon/4669747)
(6) The Orion Nebula. Credit: NASA
