TelescopesTelescopes

Mr. HibbettsMr. Hibbetts

Special thanks to Dr. Dan Bruton, Special thanks to Dr. Dan Bruton, Astronomy and Physics SFAAstronomy and Physics SFA

Telescope OpticsTelescope OpticsLensesLenses

MirrorsMirrors

Refraction...Refraction...

……is the bending of light rays upon is the bending of light rays upon passing from one transparent medium passing from one transparent medium to another.to another.

ConvexConvex and and concaveconcave lenses refract lenses refract light.light.

Reflection...Reflection...

……is the rebounding of light rays off a is the rebounding of light rays off a smooth surface (diffuse or specular).smooth surface (diffuse or specular).

ConvexConvex and and concaveconcave mirrors reflect mirrors reflect light.light.

Convex – bending or curving outwardConvex – bending or curving outward

Concave – bending or curving inwardConcave – bending or curving inward

Focal PointFocal Point the place where light rays converge to a pointthe place where light rays converge to a point

Focal LengthFocal Length the distance from a curved mirror or lens to its the distance from a curved mirror or lens to its

focus focus

Types of TelescopesTypes of TelescopesRefracting Telescope Refracting Telescope Reflecting TelescopeReflecting TelescopeCassegrain TelescopeCassegrain Telescope

Refracting TelescopeRefracting Telescope (Galilean) (Galilean)

objective lens objective lens

Eyepiece lensEyepiece lens

Typical Small RefractorTypical Small Refractor

Reflecting Telescope Reflecting Telescope (Newtonian)(Newtonian)

a concave primary mirrora concave primary mirror

flat secondary mirrorflat secondary mirror

eyepieceeyepiece

6-inch Newtonian Telescopes6-inch Newtonian Telescopes

Earl of Rosse’s LeviathanEarl of Rosse’s Leviathan

Cassegrain TelescopeCassegrain Telescope

a concave primary mirrora concave primary mirror

a convex secondary mirrora convex secondary mirror

eyepiece lenseyepiece lens

SFA ObservatorySFA Observatory

Cassegrain TelescopesCassegrain Telescopes

41” Telescope41” Telescope

18” Telescope18” Telescope

10-inch Schmidt-Cassegrain10-inch Schmidt-Cassegrain

Multiple Mirror TelescopeMultiple Mirror Telescope

Types of TelescopesTypes of Telescopes

What are the 3 types of What are the 3 types of Telescopes?Telescopes?

Why use a telescope?Why use a telescope?

BrightenBrightenMagnify Magnify ResolveResolve

Light Gather PowerLight Gather PowerHighLow

ResolutionHighLow

Magnification

HighLow

Light Gathering PowerLight Gathering Power

10.7 cm camera

15.2 cm camera

Telescopes MagnifyTelescopes MagnifyMagnificationMagnification - the number of times - the number of times

larger an object appears through a larger an object appears through a telescope than as seen by the naked telescope than as seen by the naked eyeeye

Eyepiece theofLength FocalMirroror Lens Objective theofLength FocalionMagnificat

ResolutionResolution

What makes a telescope What makes a telescope great?great?

Light Gathering PowerLight Gathering PowerLarge DiameterLarge Diameter

MagnificationMagnificationLong focal length for the primary lens or Long focal length for the primary lens or

mirrormirror Resolving PowerResolving Power

Large diameterLarge diameterQuality Lenses / MirrorsQuality Lenses / Mirrors

Why use a telescope?Why use a telescope?

BrightenBrightenMagnify Magnify ResolveResolve

On Earth, there are two major types of On Earth, there are two major types of telescopes used:telescopes used:

Common Optical TelescopesCommon Optical TelescopesRadio TelescopesRadio Telescopes

The The Earth’s atmosphereEarth’s atmosphere is mostly is mostly transparent for transparent for visible lightvisible light and and radio radio waveswaves..

Earth’s AtmosphereEarth’s Atmosphere

The Hubble Space The Hubble Space Telescope...Telescope...

……is the largest telescope in space.is the largest telescope in space. ...is 30 times more sensitive than ...is 30 times more sensitive than

ground based telescope.ground based telescope. ...orbits the Earth every 95 minutes....orbits the Earth every 95 minutes. ……gives gives high resolutionhigh resolution images because images because

it does not suffer from the effects of it does not suffer from the effects of atmospheric turbulence.atmospheric turbulence.

M100M100

Cat’s Eye NebulaCat’s Eye Nebula

Hubble Deep FieldHubble Deep Field

Kepler TelescopeKepler Telescope Launched in March 2009Launched in March 2009

Mission is to find Earth-like planets Mission is to find Earth-like planets around other starsaround other stars

Has the most resolute camera every Has the most resolute camera every constructedconstructed

Has confirmed hundreds planets Has confirmed hundreds planets and found over 2,300 candidatesand found over 2,300 candidates

Mission officially ended in August Mission officially ended in August 2013 after two motors failed2013 after two motors failed

Chandra and SpitzerChandra and SpitzerOther important NASA telescopesOther important NASA telescopesFocus on X-Ray / Gamma Ray imagesFocus on X-Ray / Gamma Ray images

Observing ProblemsObserving ProblemsWhat are some problems that prevent What are some problems that prevent

good telescope viewing?good telescope viewing?

Observing ProblemsObserving Problems Bad WeatherBad Weather Light PollutionLight Pollution DispersionDispersion ScintillationScintillation

a.k.a. “bad seeing”a.k.a. “bad seeing”This effect can be reduced with adaptive This effect can be reduced with adaptive

optics.optics.

SeeingSeeing is the measure of the steadiness of is the measure of the steadiness of an object in the Earth’s atmosphere during an object in the Earth’s atmosphere during astronomical observations.astronomical observations.

Adaptive OpticsAdaptive Optics allows astronomers to allows astronomers to correct for atmospheric distortions in correct for atmospheric distortions in images.images.

Mount Wilson ObservatoryMount Wilson Observatory

The 100” TelescopeThe 100” Telescope

Writing AssignmentWriting Assignment Imagine you are explaining the telescopes Imagine you are explaining the telescopes

you just demoed to a friend or family you just demoed to a friend or family member. Explain how they enhanced your member. Explain how they enhanced your vision and any interesting things you vision and any interesting things you noticed. noticed.

Which optic device did you find to be the Which optic device did you find to be the most useful and like the most? Explain most useful and like the most? Explain your reasons why.your reasons why.