Scottish mathematician who published an earlier design
Plate 047
1668
Cambridge and London, England
No photograph is shown for this exhibition. The museum displays an image only where it can show the object honestly.
About this date
Isaac Newton built a working reflecting telescope in 1668 and presented one to the Royal Society in 1671. James Gregory had described a design in 1663.
About credit
Gregory’s design came first on paper, but Newton built the first working instrument.
Chapter II
The world before
Life before the Reflecting Telescope
Lens telescopes had to be very long to reduce colour fringes, which made large ones unwieldy.
II
The human achievement
How it came about
Newton ground a metal mirror, placed a small flat mirror to send the light out the side, and built a telescope about 15 cm long that matched a refractor several feet in length. The Royal Society elected him a Fellow after seeing it.
III
Understanding the invention
How it works
The Reflecting Telescope, explained in two steps.
01
Step 01 of 02
Mirrors do not split colours
Reflection bends all colours the same way, so no coloured fringes.
Mirrors do not split colours
Folding the light path
IV
The transformation
What changed for humanity
Astronomy
Larger apertures revealed fainter objects.
Optics
Mirror-grinding became a specialised craft.
Almost every large professional telescope since has used mirrors, from the Hubble Space Telescope to the James Webb Space Telescope.
V
Before and after
Life before and after The Reflecting Telescope
Before
Many metres of tube and a coloured edge.
After
A compact tube with a clean image.
On larger screens, drag the divider (or use the arrow keys) to give more room to the world before or after.
