I’ve been researching the three types of stargazing telescopes in order to narrow down my choices for a good, first telescope.
The three types are:
- Refracting telescopes (lenses)
- Reflecting telescopes (mirrors)
- Also known as Newtonian telescopes after Isaac Newton
- Catadioptric telescopes (which combines both lenses and mirrors)
- Schmidt-Cassegrain or SCT and Maksutov-Cassegrain
I’ve eliminated the catadioptric telescope from the running as I want a good but reasonably-priced telescope. The catadioptrics are more costly than the other types and have lower-quality images when compared to the other two equivalently-powered scopes.
The refractive telescopes are what most people think of when telescopes are mentioned. They can be found anywhere from toy and department stores to finer telescope stores and the quality varies widely.
Beware of cheaply-made refracting telescopes with 60mm lenses that are usually advertised as a good starter scope for a child. The optical quality is usually pretty bad and you cannot see much through them which can be disappointing for a new stargazer. 70mm refractors are an improvement as long as the quality of the optics is good. Better still is an 80mm refractor that allows you to see celestial bodies of all kinds, though you should avoid plastic casings and poor-quality craftsmanship.
The main disadvantages of refractors are the chromatic aberrations or false colour from the lenses and the price compared to an equivalent reflector.
One of the advantages of refractors is the additional light allowed into the telescope since they don’t have a mirror obstructing the tube as do the Newtonians. Due to the increased light available to refractors they display higher-contrast images.
Another advantage is that the tube of the refractor telescope is sealed whereas reflectors are open to the air. Over time, the mirrors in reflectors can get dusty or show wear and will require maintenance.
Reflector scopes are bigger and can be heavier than refractors, but you get a better value for your dollar. The price for equivalent refractors will be higher and the optics in the reflector will be better.
Another reflector option: The Dobsonian telescope
In the 1960s, an amateur astronomer called John Dobson created a design for a simple DIY Newtonian-style telescope called a ‘Dobsonian’. These telescopes are made with simple materials and basic tools and once you invest in the 2 mirrors and the eyepiece, you can use a cardboard tube or wooden box to mount your mirrors and keep them in alignment.
The image from a Dobsonian is bright and clear and you can design the telescope to your own specifications. They are dubbed ‘light buckets’ as you can make them with massive apertures and with standard mirror diameters of 6-16” or much larger. These large apertures bring much fainter celestial bodies into view. The definite advantage of a Dobsonian is the cheap cost and high-image quality.
The disadvantages of a Dobsonian telescope are that they are large and difficult to move, and the mounts are simple Altitude (north/south) and Azimuth (East/West) so they are not able to track stars across the sky. I will discuss tracking celestial objects in a future post and you can follow the link below if you want more information.
Some useful links about Dobsonian telescopes: