The following table shows common scope apertures listed, both in
inches and millimeters, with the associated Light Grasp, Magnification
limits and Limiting Visual Star Magnitudes.
Refractors are what most people identify with the word "telescope".
A refracting telescope has a long narrow tube though which light
passes in a straight line from the objective lens to the eyepiece
at the lower end of the tube. Refractors have the advantages of
simplicity, reliability, low maintenance and excellent thermal characteristics.
They are ideally suited for either astronomical or terrestrial observing.
Our refracting telescopes range in diameter from 60mm to 150mm.
Larger than 150mm aperture, refractors become quite expensive. Above
this aperture category (150mm), it is more cost-effective to purchase
a Newtonian reflector.
Key Benefits:
- Reliable and easy to use due to simplicity of design.
- Unobstructed design for maximum definition.
- Rugged and virtually maintenance-free.
- Excellent for lunar, planetary and binary star observing.
- Closed tube design eliminates image-degrading air currents.
- Excellent starter telescope for discovering the wonders of the
universe.
Achromatic Refractors Achromatic refractors
are the most common type of entry-level telescopes. They are relatively
inexpensive and give good views of the moon, planets and daytime
terrestrial objects.
Apochromatic Refractors 
One of the problems with ordinary achromatic refractors is color
aberration which is a rainbow effect seen at high powers. This happens
because, as light passing through a lens, not all the frequencies
of light (colors) come to focus at the same point. Apochromatic
refractors solve this problem by using exotic glass or extra lens
elements to solve the color aberration.
Apochromatic systems are found in "high-end" refractors and produce
excellent, lunar, planetary and stellar images. |
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