Stepping into the world of Astronomy? Fantastic! There are some things to consider before purchasing a telescope. It’s a really good idea to join a forum where you can discuss, share and ask questions. Grab some magazines and even join a local astronomy club! Tag along on their observation session and you’ll be surprised at how much you can learn.
Types of Telescopes
1. Refractor Telescopes
Refractor telescopes use an objective lens to gather light. It gathers more light than what human eyes are capable of and focused it onto the eyepiece. It is reasonably durable and capable of delivering bright and detailed images because it has no obstruction (mirror). Did you know that refractors with smaller diameter can perform as well as a reflector one size bigger? This type of telescope usually is priced higher than reflector because it uses optical glass. Refractor suffers from chromatic aberration or colour fringing.
- Durable – no problem with transport.
- Excellent to view the moon, planets and stars
- Bright and high contrast images
- Heavier and Longer
- Chromatic aberration tendency – minor colour fringe
- Good refractor cost more than others
2. Reflector Telescopes
Reflectors has no objective lens, they are built with curved mirrors to reflect light. How does it work? A large concave primary mirror focuses the light, reflects it to a small secondary mirror and that little mirror redirects the focused light to the eyepiece. The most popular type of reflectors are the Newtonian and Dobsonian. The Newtonian Reflector is inexpensive and they don’t have colour fringing problem, but they suffer from coma aberration. Dobsonians are great value-for-money telescopes because it delivers extremely bright and detailed images through a simple tube design. However, Dobsonian Telescopes can be quite bulky.
- Excellent for deep sky object (nebulae, galaxies, star clusters)
- Good reflectors are affordable
- Work well even if the mirrors are slightly dusty
- Not as durable
- Coma aberration – not good for stars
- May require more care and maintenance
3. Schmidt-Cassegrain Telescopes
Cassegrain (catadioptric) telescopes use a combination of a lens (dioptric) and two mirrors (cataoptrics). There are two common types of Cassegrain telescopes, the Schmidt-Cassegrain and the Masutov-Cassegrain. The use of lens and mirror greatly reduced the aberrations that the refractor and reflector are suffering from.
Schmidt-Cassegrain – this telescope uses a thin and light corrector aspheric lens with the secondary mirror mounted on an adjustable cell in the centre of it.
Maksutov-Cassegrain telescopes use a much thicker and heavier lens. The front and back are ground as segments of a circle with different amounts of curve. The front of the lens is concave and the rear is convex and the secondary mirror is a silvered spot on the rear. Permanently on the same spot, therefore there is no need to adjust it.
- Durable and Shorter tube – no problem with transport.
- Excellent to view the moon, planets, stars and deep sky objects. (correct chromatic and coma aberrations)
- Versatile and great for astrophotography
- More expensive than reflectors of similar specification