Reflecting telescopes have been used for a long time now. They
were first invented in the 17th century and are sometimes called
a reflector which has led to confusion with the reflecting and
refracting telescope. The refracting telescope precedes the
reflecting telescope but it is rarely used and most telescopes
used today are of the reflecting type.
This is because refracting telescopes suffer from chromatic
aberrations, a result of the different refractive indexes on
the lenses in such telescopes. What this means is that around
each image, color fringes appear. While this can be reduced
it is easier to use a reflecting telescope.
Design Considerations
The first reflecting telescope to solve the problem of chromatic
aberrations was a telescope invented by Sir Isaac Newton. The
Newtonian design for reflecting telescopes is still in use today
and is one of the simplest designs of modern telescopes available
today. It is also one of the least expensive telescopes. Anyone
deciding to make their own telescope would be able to put together
a reflecting telescope of this kind.
The Cassegrain or Classic Cassegrain telescope is also very
popular and this is in part because of its compact design. This
is achieved by folding the optics in the telescope. While the
design does lose some light gathering power it has an advantage
with a closed tube that stays clean all the time.
Most professional telescopes follow the Ritchey-Chretien design.
It is an offshoot of the Cassegrain design and has two hyperbolic
mirrors. This design characteristic differs from the Cassegrain,
which employs one parabolic primary mirror instead. This kind
of telescopic lens is ideal in photography.
Another reflecting telescope that is used is the Yolo. One
of the problems associated with this telescope is that of astigmatism.
This can lead to double vision and certain blind spots. This
can be corrected however and one of the advantages of this telescope
is the fact that it eliminates the problem of coma, a problem
prevalent in many telescope designs.
Depending on your specific needs there are different types
of reflecting telescopes that would best fit your specifications.
For amateur telescope building and astronomy starting with a
Newtonian telescope is a good place to start.
It is also the least expensive kind and a good starting point
when you are just beginning to explore the world of telescopes.
Once you have ignited your passion there are many other designs
that you can try out for star gazing and wide field observation.
