A Primer on Types of Telescope Designs:
There are three basic designs of telescope.
Refractors:
The refractor is the design the average person identifies with the word “telescope”. A long thin tube that has a lens at the front end that collects the light from the front objective lens directly to the eyepiece at the opposite end of the tube..
- These scopes are easy to use and reliable due to simplicity of design and good for lunar, planetary viewing.
- Also good for distant terrestrial viewing. High contrast images.
Newtonian Reflectors
Newtonian usually use a highly polished curved mirror called the primary mirror to collect and focus incoming light which then reflects the image onto a flat secondary (diagonal) mirror that in turn reflects the image out of an opening at the side of the main tube and into the eyepiece.
- Lowest cost per inch of aperture compared to refractors and catadioptirccs since mirrors can be produced at less cost than lenses
- Good for Lunar and Planetary and deep space.
- Bright Images and can be reasonably portable
Dobsonian Telescopes
Most Newtonian Telescopes have been supplied on Equatorial mounts. The last few years has seen a new commercial telescope available in the market-the Dobsonian. A Dobsonian is a simple Altazimuth mounted Newtonian telescope. These mounts do not have any means of tracking a sky object, so can often be difficult for a novice to use. However, they are cost effective.
Catadioptric
Catadioptric use a combination of mirrors and lenses to fold the optics and form the image. There are two popular designs: the Schmidt Cassegrain and the Maksutov-Cassegrain. In the Schmidt-Cassegrain the light enters through a thin reflected mirror back up the tube and is intercepted by a small secondary mirror which reflects the light out an opening in the rear of the instrument where the image is formed out of the eyepiece.
- Generally more expensive than Newtonian of equal apertures
- Extremely compact and portable
- Easy to use
- Very Versatile
- Good for Photography
Power (Magnification)
One of the least important factors in purchasing a telescope is the power. Power, or magnification of a telescope is actually a relationship between two independent optical systems 1) The telescope itself 2) the eyepiece (ocular) you are using.
All telescopes have practical upper and lower limit's of pwer. these are determined by the laws of optics and the nature of the human eye.
Do not believe manufactures who advertise 375 or 725 power telescopes. This is generally false and misleading.
Most of your observing will be done with lower to mid range powers, the images will be much brighter and crisper providing more enjoyment and satisfaction with the wider fields of view.
Telescope mounts
Which Type of Mount should you Use?
There are two major types of mounts for astronomical telescopes:
- Altazimuth: the simplest type of mount with two motions, altitude (up and down, vertical) and azimuth (side to side-horizontal). Good Altazimuth mounts have slomotion controls which allow you to make precise tracking adjustments.
- Equatorial: superior for astronomical observing over long periods of time. As the earth rotates around its axis, the stationery stars appear to move across the sky. A telescope on an equatorial mount will more easily track and follow the object. A telescope on a Dobsonian mount will quickly float out of the field of view on both axes.
Any Further Questions?
If you need assistance in choosing the correct telescope we invite you to visit our showroomTOV speak personally with one of our Staff members all of whom are amateurs astronomers and use telescopes on a regular basis. Our combined knowledge of instruments is well over 60 years in the Telescope business.
We are genuinely interested in ensuring you purchase the right telescope to suit your needs. We offer a vast selection of instruments, the largest in Canada, to suit virtually any budget or level of experience.