Newtonian Telescope

[Vijay]

Sir Isaac Newton and the Newtonian Telescope
The seventeenth century was a golden time for astronomy and
telescopes. The very first refractors had began to appear on the scene
and were improved by Galileo and so had the very first reflector
telescopes. Like the predecessors of both models, the major flaw lay
in shaping the optics correctly, and – like Galileo – Sir Isaac Newton
was a far more advanced optician. While Galileo chose to work with
lenses, Newton chose to work with concave mirrors to gather and focus
light and his improved method came to be known as the Newtonian
Reflector Telescope.
The first Newtonian Telescope appeared in about the year 1668, and
introduced the one design manifestation that no one could figure out
how to get around – once the light was gathered by the parabola and
refocused back to a point on the focal plane, how did you view it
without obstructing the light gathering source? Newton's plan was
simple and elegant. He simply introduced a very small, secondary
mirror at the focal point and aligned it with the center of the
parabola where most incoming parallel light rays are less effective.
Held in place by thin vanes called the "spider" assembly, this
secondary mirror captured the refocused light path in a non-magnified
way and was aimed at a porthole on the top side of the optical tube.
From there a series of lenses, called the eyepiece, is used to focus
on the secondary mirror and study the image. The first practical
working model of the Newtonian Telescope went into production in
roughly the year 1689.
The Newtonian Telescope is a simple and elegant design which has
endured through the years!