There are three main types of optical telescope in common amateur usage. Each of the designs trades size and weight against portability and aperture size against cost. Other factors to take into account are the ease of use and the level of maintenance required to keep the telescope in best working order.
We are going to evaluate each of these scopes looking at portability, economics, maintenance, image detail and the type of viewing the design is best for in order to help guide you in your telescope choice.
Refracting telescope
A refracting telescope conforms to the traditional image of a telescope as a long, tube with a lens at each end. The larger objective lens, farthest away from the viewer, gathers the light and focuses it to a sharp image at the eyepiece, or ocular lens where it can be seen by the viewer. The eyepiece has various magnification elements and is able to focus the image by sliding elements in and out of the main body of the telescope
- Pros
- Easiest to use
- Very little maintenance
- Sharp images
- Cons
- Larger aperture lenses are very expensive
- Larger aperture refractors are very long and cumbersome
- Color fringes on some objects
- Ideal for planets, the moon and bright stars
Reflecting telescope
Uses one or more curved mirrors to reflect light onto an eyepiece where an image is formed for the viewer. A classic Newtonian reflector has a concave mirror at the back of the telescope which reflects onto a second, flat mirror in the center of the telescope body which then reflects the light sideways into an eyepiece mounted on the telescope body rather than the end. Several other designs exist such as the Cassegrain reflector which has a second mirror that reflects the light backwards through a small hole in the center of the primary mirror to an eyepiece mounted on the end of the telescope as with a traditional refractor.
- Pros
- Largest aperture per dollar
- Best for faint deep sky objects
- Cons
- Requires regular maintenance and collimation
- Often big and bulky
- Less sharp and lower contrast
- Ideal for galaxies, stars and deep-space objects
Catadioptric telescope
Constructed using a combination of lenses and mirrors to get the best of both worlds. Catadioptric telescope designs such as the Schmidt-Cassegrain or Maksutov ‘fold’ the optical path within the telescope to keep the size and weight down. Their design makes them rugged but due to the complex optics they are expensive to produce and suffer from taking a long time to cool down to ambient temperature and stabilize the viewing image.
- Pros
- Great all-rounder
- Most compact design
- Requires infrequent maintenance and collimation
- Cons
- Expensive design and optics
- Long time to cool to ambient temperature
- Narrower field of view
- Ideal for mixed viewing of planets and deep space objects.
Now you have asked yourself the key questions and covered the telescope types that provide the best match for your requirements, it is time to look at some telescope prices to help fix your budget.
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