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A refracting telescope is the most common kind of telescope. Discover the difference between refracting and reflecting telescopes in this free video on home astronomy from a telescope salesperson.
An apochromatic telescope features an apochromatic lens that has a better correction for chromatic aberration than achromat lens.
This type of telescope provides a better quality image than the achromat telescope. This becomes very noticeable when observing very bright celestial objects, such as Moon and Venus.
Like all refractors, apochromat is a great telescope for observing stars and planets.
It is also a great telescope for beginners in astrophotography.
Apochromatic telescopes are more expensive than achromatic telescopes. The main difference between apochromat and achromat is in their ability to correct light so that different colours lie in the image plane together.
Apochromat lens corrects light so that three colours lie in the image plane together,
while achromat lens corrects only for two.
The apochromatic telescope can become very pricey if the user wishes to have a larger aperture.
The achromat lens brings only blue and red light to the center on the same plane. The apochromat lens, on the other hand, corrects all wavelengths to focus on the same point (red, blue, and green).
An apochromat lens consists of three different types of glass:
two crown glasses,
and one flint glass.
glasses are cemented together or have an air-gap between them, or a
combination of both. Because of a higher number of glass elements, other
defects such as coma and spherical aberration also have better correction.
APO vs ED
ED refers to a range of glasses with varying levels of Fluorite content.
Nearly all apochromatic refractors use one or more elements of ED glass
so both terms correctly apply to many telescopes. Some use ED glass but
fail to achieve apochromatic performance - to those, only the ED term
The refractor telescope uses a lens to gather and focus light. The first
telescopes built were refractors. The small telescopes sold in department
stores are refractors, as well as, those used for rifle scopes.
Though excellent refractors are still made, the disadvantages of the
telescope have blocked the construction of very large refractors for use in
Observers who want the best possible image quality