Telescope Viewing Techniques

• see also:
  • astronomy index and links
  • astronomic viewing - seeing, light pollution

Telescopic viewing techniques:

• ensure your eyes are dark-adapted:
  • see vision
• averted vision:
  • By looking to one side of an object, your eye uses it's averted vision. The object is seen by a different part of the eye using your rods instead of the less sensitive cones, thereby picking up some details otherwise not seen looking directly at it. In astronomy averted vision can become a skill. Experiment with it sometimes and it will become easy.
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• use an occulting bar:
  • bright objects such as planets can make it very difficult to see their much fainter moons adjacent to them.
  • one technique is to create a linear obstruction across the eyepiece focal point (eg. where the aperture stop inside is placed) to obstruct the light from a centrally placed planet
• use filters:
  • choosing the correct filter may increase contrast and make details more visible
  • orange, yellow, red and even blue filters are commonly used to enhance details on Mars
  • "nebula" filters which block out light pollution act to make the sky background appear darker and thus creating more contrast to enable faint nebulae to be seen.
• optical correction devices:
  • "fast" Newtonian reflectors tend to have spherical aberration producing coma
    • special eyepieces can help to reduce these aberrations
    • eg. Tele-Vue's Paracorr - claims to increase diffraction limited field area by 36x & acts as a photographic field flattener.
  • field flatteners can help with the curved focus fields of Schmidt-Newtonians
  • low altitude objects are subject to atmospheric dispersion which causes blue light to be refracted up and red light to be refracted downwards causing colouration of the image.
    • a color filter can help to reduce this
    • alternatively a wedge prism or better still a Dall Transfer Lens which allows alteration of lens elements to cope with different altitudes.
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