learning hub

Guide to Choosing the Right Telescope

If you want a “telescope” for daytime viewing of land or sea then we suggest you purchase a Spotting Scope—we have several options in store.

Astronomical (star-gazing) Telescopes are not as simple as spotting scopes so we have produced this guide to help you in your buying decision.

The most important specification of any telescope is the aperture (objective) which is the diameter of the main lens or mirror of the telescope. More aperture makes for a brighter image but bear in mind that on most nights the detail you can see will be limited by atmospheric conditions.

Magnification is not important for astronomy but can be calculated by simply dividing the focal length of the telescope by the focal length of the eyepiece. The addition of a Barlow Lens can increase the magnification. The “highest practical power” is calculated using the shortest eyepiece supplied in the box.

Telescope types

Refractor

Refracting telescopes are more expensive as they use lenses to form the image. Their eyepiece is located at the rear of the telescope. Refractors produce an image that is reversed or "inverted" - no problem for astronomy but a nuisance for terrestrial observing. An erecting prism will correct the image.

Reflector

Reflecting telescopes use a mirror, instead of a lens, to form the image and the eyepiece is located at the top side of the main tube.  A reflector costs the least per inch of aperture compared to refractors and catadioptrics since mirrors can be produced at less cost than lenses. They are not suited for terrestrial applications.

Reflectors may require a little more care and maintenance because the tube is open to the air, which means dust on the optics even if the tube is kept under wraps.

Compound (catadioptric)

These use a combination of lenses and mirrors, offer compact tubes and are relatively light weight. The two popular designs you'll often see are called Maksutov-Cassegrains (MAK) and Schmidt-Cassegrains. They are more expensive than reflectors of equal aperture but their closed tube design reduces image degrading air current.

Astrophotography

An Apochromatic Refractor such as our Sky-Watcher TR102AS is recommended

Telescope Mounts

Telescopes are supplied with a mount for stabilising and included in the price. The type of mount determines how easy it is to follow a star while viewing it.

Altazimuth mount  - is a simple design that just swings up, down, left and right. The better Altazimuth mounts have slow-motion knobs for making precise adjustments, aiding smooth tracking across the sky. Not easy to follow Astronomical objects which move in arcs around the pole.

Equatorial mount – this allows users to follow the rotation of the sky as the Earth turns so easy to follow stars, planets, and other astronomical objects. However they are heavy and trickier to set-up, with a steeper learning curve for beginners

Computerised Mounts - Some telescopes come with small motors to move them around the sky with the push of a keypad button. In the more advanced models of this type, often called"Go To" telescopes, a small computer is built into the hand control.
Once you've entered the current date, time, and your location the scope can point itself to, and track, thousands of celestial objects.
Go To scopes aren't for everyone — the setup process may be confusing if you don't know how to find the bright alignment stars in the sky.


View our TELESCOPE selection here.

We'd love to see you.

visit our store