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Telescopes Part 1: Telescopes vs Spotting Scopes vs Binoculars

Telescopes, spotting scopes and binoculars - the first choice a first time telescope buyer is to decide which of these is best for your needs. Our handy guide below will aim to make this choice much easier for you.

 

Suitable for Astronomical Viewing?
(Stuff in the sky!)

Suitable for Terrestrial Viewing?
(Land, sea, birds, whales, etc.)

Binoculars

Limited

Yes!

Spotting Scopes

Limited

Yes!

Refractor Telescopes

Yes!

Limited

Reflector Telescopes

Yes!

No

Cassegrain Telescopes

Yes!

No

Telescopes

Telescopes (whether they be refractor, reflector or Cassegrain) are designed primarily for astronomical viewing. These usually have a larger aperture, making them more capable of seeing objects in low light. While refractor telescopes can be used for terrestrial viewing, their optical design actually means that the image is flipped upside-down and mirrored the wrong way around! This has little impact on astronomical use, but may limit terrestrial viewing.

Telescopes generally have a larger aperture and higher magnification than a spotting scope or pair of binoculars, allowing you to see fainter objects with greater detail.

Spotting scopes

A Spotting Scope is a special type of telescope that is far better at viewing objects on land or at sea than a conventional telescope. If you're after a telescope for terrestrial use, we strongly recommend using a spotting scope instead - its optics corrects the orientation of the image. Some spotting scopes can be used for astronomical viewing, however this is usually limited to simply seeing the craters of the Moon and getting a closer look at constellations.

The optics for spotting scopes are oriented the right way up and have a built-in zoom lens, which makes it easier to find and track objects than with a telescope. Compared to a pair of binoculars, they have a larger aperture for low-light conditions and a higher magnification for more detailed viewing.

Binoculars

Lastly, Binoculars are smaller and much more portable, making them perfect for travellers, bushwalkers, animal watchers and the like. Like spotting scopes, some binoculars are suitable for looking at larger or brighter astronomical objects. Binoculars are more portable than both spotting scopes and telescopes for people on the go!

Important Terminology

Aperture

It's probably no surprise, but a telescope works by gathering light. The diameter of the objective lens or primary mirror of any optical instrument is known as the aperture, and this defines how much light it gathers. Wider apertures let in more light, allowing more details and fainter objects to be seen. The exact same thing happens with the pupils of your eyes at night time: your pupils widen to let in more light so you can see things more clearly in the dark.

On binoculars and spotting scopes, the aperture (or object lens) size is given as the second number in the model name. For example, a 10x25 pair of binoculars has a 25mm aperture.

Telescopes normally show the aperture in the model number, usually in millimetres or inches. For example, the StarView 150EQ has a 150mm aperture, while a Celestron 8SE has an 8" (or 203.2mm) aperture.

Magnification

The magnification (or power) of any optical instrument is explained as a number of "times", such as 8x or 70x. For binoculars and spotting scopes, this is displayed in the model name - like above, a 10x25 pair of binoculars has a 10x magnification.

Telescopes are a little trickier - their magnification is determined by the size of the eyepiece that you are using, and most of our telescopes come with one or two different eyepieces. Though, contrary to what you'd think, a smaller size eyepiece will actually give you a higher magnification! The magnification is calculated by dividing the telescope's focal length with the size of the eyepiece.

Telescope Magnification Formula

Higher magnification is not always better!

Higher magnification may get you a closer look at an object, however this comes at the cost of a lower field of view. This means that an object will take up more of your telescope's view, so you may not be able to see the object in its entirety. This is especially true for objects like the Moon, and some deep sky objects like nebulas, star clusters and galaxies. Compared to a lower magnification with the same aperture, a higher magnification will also produce a slightly darker image and it may be harder to keep the image stable.

When to use a higher magnification: when viewing planets with a telescope or after locating an object with binoculars at a lower magnification.

When to use a lower magnification: when viewing deep sky objects with a telescope, to find distant objects before zooming in, or when viewing sporting events with binoculars.

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