Gregorian telescope facts for kids
A Gregorian telescope was the first type of telescope ever designed to use mirrors instead of lenses. It was invented by an English astronomer named John Gregory.
Even though John Gregory designed this telescope in 1663, it wasn't the first reflecting telescope to actually be built. Another design, called Newton's telescope, was built earlier in 1668. The first Gregorian telescope was finally built in 1673 by Robert Hooke.
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How the Gregorian Telescope Works
This telescope uses two special curved mirrors.
- The primary mirror is large and shaped like a bowl (concave). It gathers light from space.
- The secondary mirror is smaller and also bowl-shaped (concave). It reflects the light gathered by the primary mirror.
The light bounces off the primary mirror, then off the secondary mirror, and finally goes out through a hole in the center of the primary mirror. This is where you would look through an eyepiece to see the image.
Gregorian vs. Cassegrain Telescopes
The Gregorian telescope is quite similar to another type of telescope called the Cassegrain telescope. Both use a large concave primary mirror. However, the Cassegrain telescope uses a small convex secondary mirror (curved outwards like the back of a spoon), while the Gregorian uses a concave secondary mirror (curved inwards like a bowl).
Images for kids
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A Gregorian telescope from around 1735
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A side view of the telescope
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An 1873 drawing showing how a Gregorian telescope works
See also
In Spanish: Telescopio gregoriano para niños
