Types Of Telescopes For Astronomy

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Types Of Telescopes For Astronomy

Types Of Telescopes For Astronomy

Fundamental Telescope Designs

The job of a telescope is to collect light, to not magnify an image (the eyepiece does that job). The bigger the target (the part that collects the light) whether or not it's a lens, in refractors, or a mirror, in reflectors, the more light the telescope will collect. The more light you'll be able to acquire, the more detail you will be able to capture, and also necessary for astrophotography, the shorter your exposures will should be to capture this detail.

Refractor Telescopes

The type of telescope most people visualize once they hear the word telescope is the 'Refractor'. This is what Galileo used for his break-through discoveries. A refractor has an objective lens on the front which passes the light straight through to the back of the tube, focusing this light at an eyepiece or for astrophotography a camera.

Advantages:

-No central obstruction (see more in the reflecting scopes), giving higher contrast.

-Due to the simple 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 objective is completely mounted and aligned there is no such thing as a need for collimation (again more on this in another article).

-Wonderful shade in apochromatic and ED (Extra Dispersion) designs.

Disadvantages:

-Costlier per inch of aperture (objective) than reflectors and catadioptric telescopes.

-Can grow to be bulky and troublesome to manage, particularly in bigger lens designs.

Newtonian Telescopes

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 makes use of 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.

Advantages:

-Lowest cost per inch of all the telescope designs.

-More light gathering energy per dollar because of the lower value design.

-Completely perfect color rendition.

-More compact design compared to a refractor of similar light gathering ability.

-Glorious contrast for planetary and lunar astrophotography and viewing in longer focal lengths.

-Can get glorious huge-discipline astrophotos and short exposures in shorter focal lengths.

Disadvantages:

-Slight lack of contrast because of the central obstruction (the flat secondary mirror) as compared to a refractor.

-Requires more maintenance, resembling collimation (mentioned in another article) which is significant for great leads to your astrophotography, though you will learn how to do this quickly with practice.

Schmidt-Cassegrain Telescopes

This is a very popular design, with a high tech look. Often known as a CAT (Catadrioptics). They use a mix of lenses and mirrors to gather and focus the light onto the eyepiece or camera. The light enters the telescope by way of a thin 'lens' called a schmidt corrector plate, goes to the back of the scope to a spherical major mirror which displays 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 is targeted onto a gap within the main mirror where the light is collected by an eyepiece or your astrophotography camera.

Advantages:

-Compact and portable.

-Low upkeep though as soon as once more collimation is required for top performance.

-Many, many astrophotography accessories available.

-Cheaper per inch of aperture as compared with refractors.

-Glorious all-round telescope, good to excellent for both visible and astrophography.

-Very good for planetary and space wall Art Print Hampshire lunar viewing and astrophotography.

-Very good to glorious for DSO (Deep Area 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.

Disadvantages:

-Costlier per inch of aperture as compared with Newtonian telescopes.

-Lack of distinction because of the central obstruction which is even bigger than that within the Newtonian scopes.

-Resulting from their longer focal lengths the field of view is smaller and longer exposures are required for astrophotography, though a lens known as a focal reducer is available which minimizes or removes this problem. The longer focal length is definitely an advantage in planetary and lunar photography.