Astronomy for beginners Astronomy for beginners

TelescopesTelescopes

By Aashman VyasBy Aashman Vyas

What are Telescopes?What are Telescopes?

A telescope is an instrument designed for A telescope is an instrument designed for the observation of remote objects by the the observation of remote objects by the collection of Lightcollection of Light

A telescope’s diameter is measured in A telescope’s diameter is measured in inches, meters or centimeters inches, meters or centimeters

Eg: A 6inch Telescope is bigger than a Eg: A 6inch Telescope is bigger than a 4inch Telescope because it can collect 4inch Telescope because it can collect more lightmore light

How do Telescopes Work?How do Telescopes Work?

Telescopes work by using a system of Telescopes work by using a system of mirrors and lenses to refract, magnify or mirrors and lenses to refract, magnify or bend lightbend light

They can be used for terrestrial viewing They can be used for terrestrial viewing and deep-space viewingand deep-space viewing

The main purpose of the Telescope is that The main purpose of the Telescope is that they make far away objects seem more they make far away objects seem more closer closer

Telescopic WordsTelescopic Words Aperture: Aperture is the size of  the main optical lens of the Aperture: Aperture is the size of  the main optical lens of the

TelescopeTelescope Counter weight: The thing that keeps the Telescope Balanced on it’s Counter weight: The thing that keeps the Telescope Balanced on it’s

TripodTripod CCD Camera: A CCD Camera converts optical brightness into CCD Camera: A CCD Camera converts optical brightness into

electrical Signals that are sent to a Computer. (Otherwise known as electrical Signals that are sent to a Computer. (Otherwise known as a Telescope image/video Camera)a Telescope image/video Camera)

Lens: An Eyepiece attached to a Telescope that lets you see stuff.Lens: An Eyepiece attached to a Telescope that lets you see stuff. Magnitude: Magnitude of a celestial body is a measure of its Magnitude: Magnitude of a celestial body is a measure of its

brightness as seen by an observer on Earthbrightness as seen by an observer on Earth Observatory: A type of domed house housing a large TelescopeObservatory: A type of domed house housing a large Telescope Electromagnetic Spectrum: The Spectrum of Light with all the other Electromagnetic Spectrum: The Spectrum of Light with all the other

wavelengths wavelengths

Types of TelescopesTypes of Telescopes

There are many types of Telescopes There are many types of Telescopes Refractor Refractor Newtonian Reflector Newtonian Reflector Schmidt-Cassegrain (falls under Schmidt-Cassegrain (falls under

Catadioptric category) Catadioptric category)

Refractor TelescopeRefractor Telescope The Refractor, is a telescope that The Refractor, is a telescope that

uses lenses to refract, (bend), the uses lenses to refract, (bend), the light that it collectslight that it collects

This refraction causes parallel light This refraction causes parallel light rays that converge at a focal point rays that converge at a focal point at the opposite end, where they at the opposite end, where they can be magnified by an eyepiececan be magnified by an eyepiece

The large lens at the front is called The large lens at the front is called the objective lens. The objective the objective lens. The objective lens is usually composed of two or lens is usually composed of two or more individual lenses that are more individual lenses that are bonded and or arranged together bonded and or arranged together to make up what is called the to make up what is called the objective lens cellobjective lens cell

The glass material used can also The glass material used can also vary which will help in the overall vary which will help in the overall performance of the objective lensperformance of the objective lens

Refractor TelescopeRefractor TelescopeAdvantages and Disadvantages Advantages and Disadvantages

AdvantagesAdvantages-Little or no maintenance and is -Little or no maintenance and is

easy to use easy to use -Reliable due to the simplicity of -Reliable due to the simplicity of

design design -Good for terrestrial viewing -Good for terrestrial viewing -Objective lens is usually -Objective lens is usually

permanently mounted and permanently mounted and aligned aligned

-Sealed optical tube reduces -Sealed optical tube reduces image degrading air currents image degrading air currents and protects the optics and protects the optics

DisadvantagesDisadvantages-Usually more expensive per inch -Usually more expensive per inch

of aperture than Newtonians or of aperture than Newtonians or Catadioptrics Catadioptrics

-Heavier, longer and bulkier than -Heavier, longer and bulkier than equivalent aperture equivalent aperture Newtonians or Catadioptrics Newtonians or Catadioptrics

-Less suited for observation of -Less suited for observation of deep sky objects such as deep sky objects such as distant galaxies and nebulae distant galaxies and nebulae because of practical aperture because of practical aperture limitations limitations

Newtonian ReflectorNewtonian Reflector The Newtonian Reflector, The Newtonian Reflector,

is a telescope which uses is a telescope which uses a spherical or concave a spherical or concave parabolic primary mirror parabolic primary mirror to collect, reflect and to collect, reflect and focus the light onto a flat focus the light onto a flat secondary mirrorsecondary mirror

This secondary mirror in This secondary mirror in turn reflects the light out turn reflects the light out of an opening in the side of an opening in the side of the tube and into an of the tube and into an eyepiece for focus and eyepiece for focus and magnificationmagnification

Newtonian ReflectorNewtonian ReflectorAdvantages and Disadvantages Advantages and Disadvantages

AdvantagesAdvantages-Excellent for faint deep sky -Excellent for faint deep sky

objects such as remote objects such as remote galaxies, nebulae and star galaxies, nebulae and star clusters due to the generally clusters due to the generally fast focal ratiosfast focal ratios

-Reasonably compact and -Reasonably compact and portable up to focal lengths of portable up to focal lengths of 1000mm 1000mm

-Low in optical abnormalities and -Low in optical abnormalities and deliver very bright imagesdeliver very bright images

DisadvantagesDisadvantages-Requires regular alignment -Requires regular alignment

(collimation) of optics in order (collimation) of optics in order to perform at its best. Badly to perform at its best. Badly aligned optics can make the aligned optics can make the image quality suffer quite image quality suffer quite dramatically. dramatically.

-The open nature of the tube -The open nature of the tube assembly could mean more assembly could mean more complicated cleaning of mirror complicated cleaning of mirror surfaces when compared to surfaces when compared to telescopes of other designs telescopes of other designs

-Generally not suited for terrestrial -Generally not suited for terrestrial applications applications

-Slight light loss due to secondary -Slight light loss due to secondary (diagonal) obstruction when (diagonal) obstruction when compared with refractors compared with refractors

Schmidt-Cassegrain Schmidt-Cassegrain In Schmidt Cassegrain designs In Schmidt Cassegrain designs

the light enters a thin aspheric the light enters a thin aspheric Schmidt correcting lensSchmidt correcting lens

The light then strikes the The light then strikes the primary mirror and is reflected primary mirror and is reflected back up to the secondary back up to the secondary mirror that reflects the light out mirror that reflects the light out an opening in the rear of the an opening in the rear of the instrumentinstrument

Schmidt's usually have shorter Schmidt's usually have shorter focal lengths thus making them focal lengths thus making them more suitable for fainter deep more suitable for fainter deep sky objectssky objects

The thinner corrector plate The thinner corrector plate means the Schmidt is faster to means the Schmidt is faster to reach thermal stability reach thermal stability

Schmidt-CassegrainSchmidt-CassegrainAdvantages and Disadvantages Advantages and Disadvantages

AdvantagesAdvantages -Best all-around, all-purpose -Best all-around, all-purpose

telescope design. Combines telescope design. Combines the optical advantages of both the optical advantages of both lenses and mirrors while lenses and mirrors while canceling their disadvantages canceling their disadvantages

-Excellent for deep sky observing -Excellent for deep sky observing or astrophotography with fast or astrophotography with fast films or CCD'sfilms or CCD's

-Very good for lunar, planetary -Very good for lunar, planetary and binary star observing or and binary star observing or photography photography

DisadvantagesDisadvantages-More expensive than Newtonians -More expensive than Newtonians

of equal aperture of equal aperture -It is not what people expect a -It is not what people expect a

telescope to look like telescope to look like -May suffer from image shift when -May suffer from image shift when

focusing due to focus design focusing due to focus design moving the entire primary moving the entire primary mirror mirror

BibliographyBibliography

The big book of Stars and Planets by The big book of Stars and Planets by Robin KerrodRobin Kerrod

Google ImagesGoogle Imageswww.aoe.com.au/telescope_types.htmlwww.aoe.com.au/telescope_types.html Ask an Astronomer.com Ask an Astronomer.com Bluebird Book’s Tell me how Bluebird Book’s Tell me how

Thank You For Watching!!!