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Stargazing June 15th ✦ 6pm-10pm
Stargazing June 15th ✦ 6pm-10pm

Tutorials

  • Binoculars for Astronomy

    Binoculars for Astronomy

    Binoculars offer a number of advantages for stargazing. They are portable, easy to use, and provide wide-field views. There are objects which can be seen in binoculars that are difficult to view with a telescope. The Pleiades star cluster or...

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  • Optical Aberrations

    Optical Aberrations

    This section describes optical aberrations, why they occur, and how they can be eliminated or minimized. More specific information on how certain optical designs deal with aberrations is described in the Optical Designs section. Spot Diagrams Optical aberrations are normally...

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  • Optical Designs

    Optical Designs

    The following section describes in detail how various optical components work to form an image in a telescope, and how they modify or correct the aberrations present. This is intended to give more information to those who want to know...

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  • Coma

    Coma

    Above: Spot diagram of a star at the edge of the field affected by coma Coma is an off-axis aberration. Stars in the center of the field are not affected by coma, but the effect grows stronger toward the edge...

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  • Spherical Aberration

    Spherical Aberration

    Spherical Aberration Spherical aberration is an axial aberration, affecting the entire field equally, including stars at the center. All telescope designs strive to eliminate or minimize spherical aberration. Normally, spherical aberration should not be visible in an optical system. But...

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  • Astigmatism

    Astigmatism

    Above: Spot diagram of a star at the edge of the field affected by astigmatism Like coma, astigmatism is an off-axis aberration. Unlike coma, it is a symmetrical aberration. For professional astronomers this can be an important distinction, since asymmetrical...

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  • Field Curvature

    Field Curvature

    The focal planes of most telescopes are not flat. Off-axis light usually focuses closer to the objective than does on-axis light. Above: A curved focal plane For visual observing, a slightly curved field is no big deal. The eyepiece will...

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  • Distortion

    Distortion

    Distortion is one of the least problematic aberrations for telescopes. Distortion is typically only large over very wide fields such as with wide-angle camera lenses. Over the small fields of view associated with telescopes, distortion is rarely an issue. Very...

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  • Longitudinal Chromatic Aberration

    Longitudinal Chromatic Aberration

    Longitudinal Chromatic Aberration Often called longitudinal color, or axial color, this is the primary aberration affecting refracting telescopes. It can also arise in any system which uses lenses, although it tends to be most problematic in pure refracting instruments. How...

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  • Lateral Chromatic Aberration

    Lateral Chromatic Aberration

    Lateral color is an off-axis aberration resulting from a difference of image scale at each wavelength. Above: Lateral color arises from a difference in image scale depending on wavelength Lateral color causes colored fringes at the edge of the field....

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  • Achromatic and Apochromatic Refractor Designs

    Achromatic and Apochromatic Refractor Designs

    Above: Optical layout of a typical refracting telescope This section details the optical design and inherent aberrations of refracting telescopes. For a more basic overview of this design please see theRefractors page. For a review of the optical design terms,...

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  • Newtonian Reflectors

    Newtonian Reflectors

    Above: Optical layout of a typical Newtonian reflecting telescope This section details the optical design and inherent aberrations of Newtonian reflecting telescopes. For a more basic overview of this design please see the Newtonian page. For a review of the...

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