Newtonian Telescopes

The First Newtonian Reflecting Telescope

The first reflecting telescope built by Newton was made with the purpose of proving conclusively that white light is made up of an array of spectrum colours, the real problem he faced was chromatic aberration (a common fault of refracting telescopes of the time) this was the puzzle to solve and later in the 1660s a breakthrough was made and Newton discovered the defect was caused by  the actual lens of the refracting telescope mimicked the behaviour of prisms thus by carrying out more experiments, he determined that chromatic aberration could be handled by merely constructing a telescope minus the lens thus the reflecting telescope was born.


Newtons first attempt at a reflecting telescope employed the best materials of the time including alloy, Tin and Copper, he found these ideal for his objective mirror and as time went on he made considerable improvements to its operation – shaping and grinding the main mirror and also polishing the optical surface itself bringing more clarity and sharpness to viewed images and also more range. The mirror itself was a spherical shape this was based on making the construction as easy and simple as possible, knowing at the same time this shape would allow spherical aberration into the equation.

Improvements to the scope were ongoing and he found that by adding a secondary diagonally mounted mirror (which proved a task in itself) near the primary mirror’s focus to reflect the image at a 90° angle to an eyepiece mounted on the side of the telescope allowed the image to be viewed with minimal obstruction and greater clarity than before. Additionally, Newton added a tube and related fittings (including a mount) to the assembly giving the primary mirror diameter of around 33mm. Through trial and error and much study, the telescope was completed and it was a milestone in astronomy of the time.


The Telescope was able to work distortion-free and moons including Galilean and Jupiter now came in to view, further planets (outlines) were observed including Venus and its related stars. With the success of this 1st scope came further advances including a second scope which was demonstrated to King Charles II I January 1662. Around the same time by invitation of The Royal Society of London, Newton became a fellow of the society joining the ranks of distinguished members with many sharing his theories and interests.

Despite barriers not limited to finance, Newton continued at a breathtaking speed with further advances through the years however one stumbling block needed to be cracked and this was to construct an effective reflector, this proved to be a considerable challenge as it proved very difficult to grind the spectrum metal to a regular curvature that could be relied upon. He noted that the surface actually tarnished very quickly thus the low reflection was very dim in comparison to more contemporary refractors, the solution to this was found, however, surprisingly the Newtonian Reflecting Telescope was not globally recognized and adopted.
Further refinements were made and with others lending a hand the Newtonian Telescope was adopted widely throughout the UK and the world.


Benefits of a Newtonian Design

Reliability is a key component here and these telescopes are used the world over. Unlike refracting telescopes, the Newtonian is free of chromatic aberration with only one surface which is very highly polished and ground, the fabrication is considerably easier than other types of scope designs.

They are way more affordable than other types of Telescopes on the market today. Easier to get a short focal ratio thus a wider view.
very portable and easy to stow

Disadvantage in the Newtonian Design
As they employ parabolic mirrors they do suffer from a coma (O/A aberration) this can be considerable and affects the photographic aspect of its use. This can be rectified but the cost may outweigh the overall price of the scope.