AstroMedia: The Newtonian reflecting telescope

AstroMedia: The Newtonian reflecting telescope

Small change, big impact
Isaac Newton (1643-1727) solved the hitherto existing problems of refracting telescopes in 1668 by inventing his reflecting telescope. He simply replaced the converging lens by a converging mirror. The light is reflected in a bundle and directed sideways out into an eyepiece by a small, slanted flat mirror. Newton´s first mirrors, which he ground and polished himself with tools he built for the purpose, were 25 and 50 mm in diameter, respectively, had a focal length of 300 mm, and could magnify about 30 times.

We can do what Newton could do
The performance of the Astro-Didactic reflecting telescope is about the same as Newton´s first homemade instruments. The centerpiece is the main mirror, a precision spherical mirror of ground and polished glass 70 mm in diameter and 450 mm focal length, specially calculated and manufactured for this kit. The eyepieces are equipped with optics made of acrylic glass. They provide 16x and 30x magnification and allow viewing of lunar craters and, with careful adjustment of the primary mirror, Jupiter´s moons. A solar filter attachment with solar filter foil is available as an accessory for observing sunspots.

In Newton´s Footsteps
While a cardboard telescope obviously can´t compete with a much more expensive massive instrument, this kit gives you the opportunity to follow in Newton´s footsteps and do all the assembly steps yourself, and in the end you´ll be as surprised by the result as Newton himself was by his first reflecting telescope.


This is what you need for the assembly

a sharp cutter knife

a good all-purpose glue

some fine sandpaper

a pair of scissors

a blunt knife for folding

a toothpick or similar to stiffen the eyepiece tube

a few paper clips

about 12 paper or document clips or simply clothespins to hold it in place

a set square or a ruler for aligning the main mirror

if available, a glass sphere for reflecting the sun.

For perfectionists:

a black felt-tip pen

a gold paint pen