Telescopes types are mainly Refractor, Reflector and Catadioptric and they are usually named in this sequence.
From these 2 types there are many similar similar or specialists like the Achromatic, Argunov–Cassegrain, Cassegrain reflector, Dobsonian, Klevtsov–Cassegrain, Infrared, Korsch, Matsukov, Newtonian, Schmidt–Cassegrain, Schmidt–Newton and many more.
REFRACTOR
A refractor or dioptric telescope basically uses 2 lenses, one each end of the telescope length and as its name says, it refracts (or bend) light and therefore the image captured.
The main one is at the opposite end from the observer eyepiece called object glass or objective lens
and it is the base or main lens to form the image and at the observer end you find the eyepiece lens.
The objective lens (the main one) collects the light and it focuses it.
The resulted image is magnified and sent to the ocular (where the eyepiece fits in) and by adjusting the focuser you actually slide the eyepiece in and out to focus the image for your view.
REFLECTOR
Reflector telescopes work in a different manner, than Refractors.
The main lens on the Reflector Telescope is fit near the observer side of the telescope tube and the light is gathered at the bottom of the telescope.
The main lens (at the bottom of telescope) is a concave mirror, also called Primary Mirror.
The way this main lens (The Primary Mirror) is prepared or shaped is the one that makes the Reflector different from one type to another.
For example one that has a small secondary mirror (usually fit at the centre on the opposite end from the observer) and it reflects the image back (near the Main Primary Mirror where a ocular is fitted with a eyepiece for the observer to view.
This type is called Cassegrain.
The Newtonian, as the word says was named after Sir Isaac Newton basic design creation.
Basically the secondary mirror is placed at a certain angle where the secondary mirror is placed on a Cassegrain and the image is sent to a lateral eyepiece – the observer is at the top end of the telescope.
CATADIOPTRIC
This telescope was a creation of the famous German astronomer Bernhard Schmidt and it is a mixture of the Refractor and Reflector.
it uses a main or Primary Mirror at the back of the telescope and a corrector (glass) at the opposite end which function was to correct spherical aberration.
From the above telescope, a new one came out:
the Matsukov, about 70 years ago (from the famous Russian astronomer D. Matsukov) and the Schmidt Cassegrain telescope – 10 years earlier.
These days it is the most popular of them for versatility and reliability on observations.
These 2 telescope (Matsukov and Schmidt-Cassegrain) are very similar, but the Matsukov has a more spherical correcting lens.
ADVANTAGES AND DISADVANTAGES OF REFRACTOR AND REFLECTOR TELESCOPES
| REFRACTOR | REFLECTOR | |
|---|---|---|
| ALIGNMENT | More stable for misalignment | Easy misalignment |
| LENS | Sealed lens – rarely needs cleaning | Frequent cleaning |
| ABERRATION | Can be high ! | Possible spherical aberration, but they do not suffer from Chromatic aberration. |
| BUILT | The way they are fit, limits the size of the mirror | Easier to build and without defects, since they use mirrors and not lenses. Large mirror can be built, therefore large telescopes can be made. |
I hope the above explanations helped you and if not, I may have just made your life more difficult – sorry !
