Fundamental Telescope Designs
The job of a telescope is to collect light, not to magnify an image (the eyepiece does that job). The larger the target (the half that collects the light) whether or not it be a lens, in refractors, or a mirror, in reflectors, the more light the telescope will collect. The more light you may accumulate, the more detail you may be able to seize, and likewise vital for astrophotography, Magnetic Levitating Lamp
the shorter your exposures will need to be to capture this detail.
The type of telescope most people visualize after they hear the word telescope is the 'Refractor'. This is what Galileo used for his break-by means of discoveries. A refractor has an objective lens on the front which passes the light straight by way of to the back of the tube, focusing this light at an eyepiece or for astrophotography a camera.
-No central obstruction (see more within the reflecting scopes), giving higher contrast.
-As a result of easy design they require little maintenance.
-Wonderful for planetary and lunar viewing and photography.
-Wonderful for large area viewing and astrophotography particularly in shorter focal lengths (more on this later).
-Because the target is permanently mounted and aligned there isn't any need for collimation (again more on this in another article).
-Glorious color in apochromatic and ED (Extra Dispersion) designs.
-Costlier per inch of aperture (objective) than reflectors and catadioptric telescopes.
-Can grow to be cumbersome and troublesome to manage, particularly in larger lens designs.
This design was invented by Sir Isaac Newton (he of the apple on the head fame). Instead of a lens at the entrance of the tube this telescope design uses a concave, parabolic mirror to gather light reflecting it back towards the entrance of the tube to a flat diagonal mirror which displays the light out the side of the telescope to the eyepiece or camera for astrophotography.
-Lowest cost per inch of all of the telescope designs.
-More light gathering power per dollar because of the lower cost design.
-Completely perfect colour rendition.
-More compact design compared to a refractor of comparable light gathering ability.
-Glorious contrast for planetary and lunar astrophotography and viewing in longer focal lengths.
-Can get wonderful huge-area astrophotos and brief exposures in shorter focal lengths.
-Slight loss of contrast as a result of central obstruction (the flat secondary mirror) as compared to a refractor.
-Requires more upkeep, resembling collimation (discussed in another article) which is vital for great leads to your astrophotography, though you will discover ways to do this quickly with practice.
This is a very talked-about design, with a high tech look. Also called a CAT (Catadrioptics). They use a mixture of lenses and mirrors to gather and focus the light onto the eyepiece or camera. The light enters the telescope through a thin 'lens' called a schmidt corrector plate, goes to the back of the scope to a spherical major mirror which reflects the light back towards the front. Here the light strikes another mirror, the secondary mirror which is mounted on the corrector plate. This secondary mirror then reflects the light back towards the back where it's centered onto a hole in the major mirror where the light is collected by an eyepiece or your astrophotography camera.
-Compact and portable.
-Low maintenance although as soon as again collimation is required for top performance.
-Many, many astrophotography equipment available.
-Cheaper per inch of aperture as compared with refractors.
-Excellent all-round telescope, good to superb for each visual and astrophography.
-Superb for planetary and lunar viewing and astrophotography.
-Excellent to excellent for DSO (Deep Space Object) astrophotography with a caveat (see the disadvantages).
-Very good to glorious optics, each Meade and Celestron are placing out glorious optics on a constant basis.
-Costlier per inch of aperture as compared with Newtonian telescopes.
-Lack of contrast because of the central obstruction which is even larger than that within the Newtonian scopes.
-Due to their longer focal lengths the field of view is smaller and longer exposures are required for astrophotography, though a lens generally known as a focal reducer is available which minimizes or removes this problem. The longer focal size is actually an advantage in planetary and lunar photography.