Telescope Viewing Techniques
- ensure your eyes are dark-adapted:
- 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.
- 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
- 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
- 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