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What is "Chromatic Aberration"?
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telescopes knowledge   Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light.

Since the focal length f of a lens is dependent on n, it follows that different wavelengths of light will be focused to different positions. Chromatic aberration of a lens is seen as fringes of color around the image, because all colors cannot be focused at a single common position on the optical axis. However, there exists a point, called circle of least confusion, where this effect can be minimized.

Chromatic aberration can be further minimised by using an achromatic doublet or achromat in which two materials with differing dispersion are bonded together to form a single lens. This reduces the amount of chromatic aberration over a certain range of wavelengths, though it does not produce perfect correction.

Also, special glasses have been developed, notably containing the mineral called fluorspar, which have such a low dispersion that using two lenses already give a very good correction.

Optical engineers can design lenses that bring several colors to a focus at the same distance from the lens. Such lenses can be apochromatic, and can give sharper images than uncorrected optics. However, it requires extra pieces of glass in the optical path, and additional kinds of glass. This makes apochromatic lenses heavier and more expensive than their uncorrected counterparts.

An apochromatic lens is often called an apochromat, or apo, for short.

 

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Telescope Designs
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subject related telelscopes   In general, there are two kinds of telescope systems. One is the Optical Telescope. This is our main manufacturing base. The other is the radio telescope, which is used for National & Scientific research . We manufacture only a few of these.
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Telescope Reviews
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  Telescope reviews from our clients and end users. Please feel free to post your own comments.
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Achromats  
4"inch/102mm short focus length achromatic telescope
Item No. DT660x102EQ5/AT5
102mm (4"), FL=660mm
details require sample
 
4"inch/102mm long focus length achromatic telescope
Item No. NDT1000x102
102mm (4"), FL=1000mm
details require sample
 
5"inch/127mm short focus length achromatic telescope
Item No. NDT635x127EQ5/ST2
127mm (5"), FL=635mm
details require sample
 
5"inch/127mm medium focus length
Item No. NDT820x127
127mm (5"), FL=820mm
details require sample
 
5"inch/127mm long focus length
Item No. NDT1200x127
127mm (5"), FL=1200mm
details require sample
 
6"inch/152mm short focus length
Item No. NDT760x152EQ5/ST2
152mm (6"), FL=760mm
details require sample
 
6"inch/152mm medium focus length
Item No. NDT990x152
152mm (6"), FL=990mm
details require sample
 
6"inch/152mm long focus length
Item No. NDT1200x152
152mm (6"), FL=1200mm
details require sample
 
4"inch/102mm short focus length
Item No. F600x102EQ-IV-A
102mm (4"), FL=600mm
details require sample
 
4"inch/102mm long focus length
Item No. F900x102EQ-IV-A
102mm (4"), FL=900mm
details require sample
 
5"inch/127mm short focus length
Item No. F700x127EQ-IV-A
127mm (5"), FL=700mm
details require sample
 
5"inch/127mm long focus length
Item No. F1200x127EQ-IV-A
127mm (5"), FL=1200mm
details require sample
 
6"inch/150mm short focus length
Item No. F750x150EQ-IV-A
150mm (6"), FL=750mm
details require sample
 
6"inch/150mm long focus length
Item No. F1200x150EQ-IV-A
150mm (6"), FL=1200mm
details require sample
 
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