Telescopes

• Refraction is the bending of light (it also happens with sound, water and other waves) as it passes from one transparent substance into another.

• Reflection is the bending of light (it also happens with sound, water and other waves) as it passes from one transparent substance into another.

Infrared telescope:

Infrared telescope can see things in the infrared wavelength.

Can see universe expansion.

Anything that has heat will affect it.

An infrared telescope is a telescope that uses infrared light to detect celestial bodies. Infrared light is one of several types of radiation present in the electromagnetic spectrum. All celestial objects with a temperature above absolute zero emit some form of electromagnetic radiation.

Radio Telescopes:

We use radio telescopes to study naturally occurring radio light from stars, galaxies, black holes, and other astronomical objects. We can also use them to transmit and reflect radio light off of planetary bodies in our solar system. These specially designed telescopes observe the longest wavelengths of light, ranging from 1 millimetre to over 10 meters long. For comparison, visible light waves are only a few hundred nanometers long, and a nanometer is only 1/10,000th the thickness of a piece of paper! In fact, we don’t usually refer to radio light by its wavelength, but by its frequency.

Naturally occurring radio waves are extremely weak by the time they reach us from space. A cell phone signal is a billion billion times more powerful than the cosmic waves our telescopes detect.

Redshift + Blueshift:

In the widely accepted cosmological model based on general relativity, redshift is mainly a result of the expansion of space: this means that the farther away a galaxy is from us, the more the space has expanded in the time since the light left that galaxy, so the more the light has been stretched, the more redshifted. Redshift and blueshift describe the change in the frequency of a light wave depending on whether an object is moving towards or away from us. When an object is moving away from us, the light from the object is known as redshift, and when an object is moving towards us, the light from the object is known as blueshift.

Reflector Telescope:

The reflector telescope uses a mirror to gather and focus light. All celestial objects (including those in our solar system) are so far away that all of the light rays coming from them reach the Earth as parallel rays. Because the light rays are parallel to each other, the reflector telescope's mirror has a parabolic shape. The parabolic-shaped mirror focusses the parallel lights rays to a single point.

Pros

• Reflector telescopes do not suffer from chromatic aberration because all wavelengths will reflect off the mirror in the same way.

• Support for the objective mirror is all along the back side so they can be made very BIG!

• Reflector telescopes are cheaper to make than refractors of the same size.

• Because light is reflecting off the objective, rather than passing through it, only one side of the reflector telescope's objective needs to be perfect.

Cons

• Reflector telescopes do not suffer from chromatic aberration because all wavelengths will reflect off the mirror in the same way.

• Support for the objective mirror is all along the back side so they can be made very BIG!

• Reflector telescopes are cheaper to make than refractors of the same size.

• Because light is reflecting off the objective, rather than passing through it, only one side of the reflector telescope's objective needs to be perfect.

Refractor Telescope:

Optical system is more resilient to misalignment than the reflector telescope, rarely needs cleaning, images are sharper and steadier than reflector telescope of same size.

Pros

• Superior revolving power per inch of aperture

• Superior performance in inferior conditions - image steadier

• Not reflections or interruption of light path

• Near permanent optical alignment - minimum maintenance

• Long focal ratios can mean use of longer focus, simpler, eyepieces

Cons

• Very high initial cost relative to reflector

• A certain amount of secondary spectrum (chromatic aberration) unavoidable (reflector completely free of this)

• Long focal ratios can mean that the instrument is cumbersome

Reflection: