Telescopes

T02 - CalubT08 - Li

T10 – Misola

Physics 3 Presentation

Definition

Telescopes – are instruments used to observe

remote, distant objects. It collects and focuses light

coming from the observed object, resulting to a clearer,

magnified image of it.

* We need magnification for our eyes don’t have enough space to see distant things.

Pixel example.

A Bit of History

• Coming from the word “tele” – far and

“skopein” – far seeing.

• Since its invention in 1608 by Hans

Lippershy, it has been widely used in

Astrophysics. Galileo was considered

the father of telescopes.

• Galileo first used a telescope for

astronomical purposes.

• Kepler improved the design further

using two convex lenses.

As of now,

from the simple

lens ancestor, it

has evolved into

gamma ray,

infrared

telescopes,

basically the

types of

electromagnetic

waves available.

• Properties– Aperture – how well it can collect light.

• Larger diameter = more light = clearer view

– Magnification• Factors affecting the performance of telescopes

in magnifying objects vary depending on the following:– Availability of Light in the Environment– Combination of Lenses/Mirrors Used

• Thickness and focal length

Parts of a Telescope

• Objective Lens – collects lots of lights and focuses it into a very small image at the focus.•Eyepiece Lens – magnifies the focused image into a size that perfectly fits into the viewer’s eyes.

Two Basic Types

• Reflecting– An optical telescope.

• Increases apparent brightness of object, and its angular size.

– Invented in the 17th Century.

– More used nowadays in astronomical labs.

– Mirror based.

• Refracting – Also an optical

telescope.– Primarily uses lenses.– Invented earlier.

Refracting Telescope

• Uses concave objective

and convex ocular lens.

•Bends parallel lights

into a focal point to

create a clearer image.

•Angular magnification is

equal to the ratio of

objective focal length over

eyepiece focal length.

•Used in binoculars.

•Pros:•Low Maintenance•Clear and contrasting Images•Ease of Usage

•Cons:• Chromatic Aberration

• Fringes or Rainbow like appearances at the points of the images where dark and light colors appear.• Because of the different wavelengths in a white light.

•Costs more.•Not developed for Astronomical Purposes.• Light loss.

Reflecting Telescope

•Commonly uses parabolic

primary mirror and angled

flat secondary mirror to

focus light into the

eyepiece.

• Famous models are

Gregorian

and Newtonian telescopes.

•Easier to manufacture,

cheaper materials and less

spherical abberations.

First model built in 1688 by Newton.

Its popularity increased with the

advent in silver coating, parabolic

mirror manufacturing,

segmented mirrors, etc.

•Pros•Cheaper to manufacture•More capable to detect faint astronomical objects.• Tends to have more compact design.

•Cons• The tube body can get easily destroyed = high maintenance.• Bulkier Design•Spherical Abberation•Higher magnification = smaller field of view

Catadioptric Telescopes

•Uses both lenses and mirrors.

•Used widely in taking highly accurate magnifications/lighting . I.e.: microscopes, headlamps, etc.

Here are other types of Telescopes

Radio Telescopes

Gemini N Mauna Kea (4213 m), Hawaii

Gemini S Cerro Pachon (2722 m), Chile

William Herschel telescope 4.2 m, La Palma (2400 m), Canary Islands, Spain

Optical and IR

References• http://science.howstuffworks.com/telescope3.htm• http://webcache.googleusercontent.com/search?

gcx=w&ix=c2&sourceid=chrome&ie=UTF-8&q=cache%3Atelescopes.lifetips.com%2Fcat%2F64000%2Frefracting-telescopes%2Findex.html

• http://webcache.googleusercontent.com/search?gcx=w&ix=c2&sourceid=chrome&ie=UTF-8&q=cache%3Atelescopes.lifetips.com%2Fcat%2F63999%2Freflecting-telescopes%2Findex.html

• http://en.wikipedia.org/wiki/Chromatic_aberration• http://webcache.googleusercontent.com/search?

q=cache:ZKn7pHGyE8EJ:www.astro-tom.com/technical_data/useful_formulas.htm+telescope+formulae&cd=1&hl=tl&ct=clnk&gl=ph

• http://www.slideshare.net/radmila/telescopes-presentation• http://www.slideshare.net/bergsa/HowTelescopesWork