Transcript Reflecting - Cloudfront.net

The Largest Telescopes
And
Telescopes made to see
Invisible E-M Radiation
Optical Mirrors & Large Scopes
Optical mirrors are silvered on the front.
So light doesn’t go through the glass. Thus…
• there is no chromatic aberration and
• imperfections in the glass do not matter as much
If parabolic there is no spherical aberration
and there is less sag
Thus the largest astronomical telescopes are all…
prime focus reflectors with parabolic mirrors
Multiple Mirror Scopes
Recently to gather more light two or more
telescopes are linked by computer.
This creates an image that is brighter and has
better resolution than either scope could
produce on its own.
The Gemini Telescopes, on the big island of
Hawaii are a pair of linked telescopes
The Largest Telescopes
For a long time the largest telescope was the one
on Mt. Palomar here in So Cal.
It has a 200” objective mirror
For a while the largest was in Russia at 236”
The Largest Telescope now is really four 8m
scopes that work together, …the VLT
Or “Very Large Telescope”
It is in Chile, so it can see things in the sky of
the Southern Hemisphere
Space Telescopes
Scintillation or “twinkling” of a star is caused
by unstable air refracting the star’s light in
different directions.
Light is also absorbed and scattered by the
atmosphere
This means that even an optical telescope works
better in Space. Like
• Hubble Space Telescope: For “Deep Space”
• Kepler Space telescope: Looking for planet
around other stars
Radio, X-ray and UV Telescopes
Radio telescopes look and work like a
satellite dish letting us “see” radio waves
The “dish” is the objective.
Infrared, UV and X-ray telescopes also let us
“see” those wavelengths
Because the atmosphere absorbs these
wavelengths they are best placed in space
Detecting Light
1. At first images in telescopes were seen by one
person and had to be hand drawn by the
astronomer to be shared.
2. In the 1800s Film Cameras became available,
though they weren’t used in telescopes until the
1900s. Objects then were photographed
3. Now Charge-Coupled Devices (CCDs) are used to
create images and are 20 times more sensitive to
light as film. Now objects are digitally imaged
Computer aided imaging
Most recently computers have been used to
alter images.
i.e.
• The light from a star can be subtracted so
that we can see the planets orbiting it.
• False color images---that let you “see”
invisible E-M waves like Infrared