Optical Telescopes

Types of Optical Telescopes There are many types of Optical Telescopes that have been developed over time in order to view objects in space more effectively.

Refractor Telescopes Refractor Telescopes are the earliest telescopes utilized. They were originally designed by the Dutch in order to see ships off of the coast but were later used by Galileo with a few adjustments in order to view objects in space.

Refracting Telescopes and Convex Lens Refracting telescopes use two lens’ within a long tube. The outer most lens is called the Objective lens this is a convex lens used to focus rays of light to one focal point. On the further side of the telescope is the eyepiece or a concave lens the concave lens that bends the light rays so that they spread out. Working together these lenses are able to take in more light than that of the human eye in order to magnify objects. These telescopes are not all together effective. When colors pass through the lens they are bent at different angels and will converge at different focus points. This distortion is called chromatic aberration and will make it so that stars appear to have a rainbow halo. This can be counteracted by adding a thin layer of a different kind of class behind the objective lens.

Refracting Telescopes Refracting telescopes are easy to maintain And sturdy and by many websites are recommended as a great beginner telescope.

Reflector Telescope Reflector Telescopes seek to resolve the problem of chromatic aberration by using mirrors instead of lenses. The mirrors will bring all different wavelengths to a common focus point.

Prime Focus Focus Point Primary mirror Prime Focus telescopes use one concave mirror called the objective mirror at the furthest end of the telescope. The light reflects off of the mirror and back to a single focus point. The problem with this is that the focus point is directly in front of the mirror and these kinds of telescopes cannot be used for commercial use because your head will be in the way but are often used with photography to capture images of the objects being observed. Primary mirror

Newtonian Reflector In order to combat the issue of the focus point of the prime focus telescope. By using a secondary mirror that is flat and tilted at an angle to reflect the focused light outside of the telescope and to an eyepiece

Cassegrain Telescope The Cassegrain Telescope uses two mirrors as well. But the primary mirror is at a deeper curve and the secondary mirror is a convex mirror also called a hyperbolic mirror. The light will enter the telescope reflect off of the primary mirror to the secondary mirror and then back to a hole in the primary mirror to the eye piece. The deeper curve of the primary mirror brings the Focal Plane in closer

Coude Telescope The Coude Telescope (Also called a Nasmyth) uses the same primary and secondary mirror structures as the Cassegrain telescopes but instead of having a hole for the eye piece there is a third mirror tilted at an angle to project the focus to the eye piece that is outside of the telescope.

Shane Telescope Was commissioned in 1959 and for a number of years was the second largestreflector telescope in the world. It is located on Mount Hamilton in California It uses 3 different kinds of foci, Prime Focus, Cassegrain Focus and Coude Focus

Gran Telescopio CANARIAS The Gran Telescopio Canarias is the largest reflective telescope in the world. It is located on the Island of La Palma (Canary Islands) part of spain. It utalizes both Cassegrain and Coude focus.

TELESCOPES

Work Sited http://spiff.rit.edu/classes/phys301/lectures/optical_tel/optical_tel.html http://www.stargazing.net/naa/scope2.htm http://lcogt.net/book/export/html/574 http://www.ucolick.org/public/telescopes/shane.html#Cassegrain http://www.vikdhillon.staff.shef.ac.uk/teaching/phy217/telescopes/phy217_tel_coude.html http://www.gtc.iac.es/GTChome.php http://www.ucolick.org/public/telescopes/shane.html