Reflector Telescopes
Reflector Telescopes - Reflecting Telescopes
Reflector telescopes are those which gather light on a mirror surface then reflect it to the eyepiece via a secondary mirror. They offer excellent deep sky views particularly from a good dark sky location.
Their simple construction makes them economic so large apertures are quite affordable and they are very easy to use. The main maintenance consideration is keeping dust off the mirror so keep the cap on your scope when not in use to minimise this. Collimation may be required from time to time, this is the process by which you ensure the mirror is correctly aligned. That maybe sounds a bit complicated but in reality it is a simple adjustment which reflecting telescope owners soon get the hang of without much thinking about it.
If you want a real big aperture, go for a Dobsonian telescope. This is simply a big reflector tube mounted on a turntable which swivels on the ground. Called Dobsonian after their developer John Dobson, a legendary figure in amateur astronomy who has helped bring astronomy to the masses through concepts like Sidewalk Astronomy. These Dobsonian telescopes are particularly easy to use so are popular with schools and clubs doing public viewing evenings. Not so easy to fit in the car though!
You will sometimes here this type of telescope referred to as a ‘Newtonian Reflector’ after its developer Sir Isaac Newton back in the 17th century. He was not actually the inventor by the way but he is generally thought to have made the first practical one.
PROs and CONs of Reflectors
PROs
Simpler construction means this type of telescope is a lot cheaper to make for any given aperture. Being cheaper to make means they are cheaper to buy!
Short focal length types provide greater field of view
No chromatic aberration such as with refractors because there are no lenses in the design so no color effects.
The eyepiece is in a more user friendly position at the top of the tube an important point when trying to view something high in the sky.
More portable than refractors of the same aperture at least at the larger apertures
CONs
Some loss of contrast inherent in the design, the support for the secondary mirror being an obstruction in the light path
Require collimation from time to time (see above) especially if transported a lot
Shorter focal length models suffer from coma which makes off center object look a little distorted. This effect is negligible above focal ratios of f/6