Webb Telescope Optics Meet Expectations

The James Webb Space Telescope team has announced that they’ve completed a key stage in deploying its primary mirror. Find out why NASA now confirms that the telescope’s audacious design will deliver on its demanding science goals.

I still have the first telescope I bought at the now defunct Efston Science store in Toronto about thirty years ago. The Edmund Scientific Company (also now defunct) produced that basic but easy to use 75mm (3 inch) Newtonian reflector.

Columnist Alex Berezov has made the case that Sir Isaac Newton was “the smartest person who ever lived.” He contributed to many fields, but for this story, we’ll focus on his Newtonian telescope design.

The Newtonian telescope uses mirrors instead of lenses. There’s a large, round, concave mirror at the back of the tube that reflects the light to a smaller mirror near the front.

Newtonian Telescope Uses Mirrors Instead of Lenses

The light then passes vertically through an eyepiece to the observer. Newton’s design eliminates the distorted colours we tend to see with lenses.

It’s also less expensive because it only needs one precisely shaped surface to work. It offers a wider field of view and you look into it from the side instead of the back end, which is usually more comfortable, at least on a backyard telescope.

These advantages have proven to be timeless. Nearly all major telescopes in observatories today are Newtonian Reflectors.

Webb Telescope Includes Bold, Fascinating Innovation

That also goes for NASA’s James Webb Space Telescope, the replacement for the venerable Hubble. Even so, the Webb Telescope includes a bold and fascinating innovation.

The 6.5 metre (21 foot) primary mirror on the Webb Telescope consists of 18 separate hexagonal segments that folded up into the rocket for launch. Each segment is 1.32 metres (4.3 feet) wide.

The Webb Telescope is 2.7 times larger than the mirror in the Hubble Telescope. It’s the…