Telescopes….
Telescopes are helpful to
astronomers because they….
• Collect more light
• Separate distant
objects….
• Magnify the image
• Detect other
wavelengths…
Telescopes and Domes
Optical Telescopes;
* use lenses and mirrors to gather and focus
starlight.
* the light gathering power depends on the
area of the lens or mirror.
There are 2 types of optical telescopes………..
Refracting…
• Has two lenses..
• Uses large objective
lens to gather and
focus light.
• Most in use today are
almost 100 years old.
Reflecting telescope…
• Uses one large
curved mirror to
gather and focus
starlight.
MMT multiple-mirror
telescope
• This telescope has
several mirrors that
take the place of one
mirror..
• Spectroscope:
separates starlight
into colors.
3 kinds of visible spectrum…
• Continuous – unbroken band of colors.
Source is sending out energy of all
wavelengths.
• Bright line – Source
is sending out only
certain wavelengths
of energy. (also
called emission
spectra)
• Dark-line – continuous
spectrum with dark
lines. Helps identify
composition.
Radio Telescope
• Collects radio waves and feeds them to
a receiver, where they are changed into
electrical signals.
• What are some advantages that a radio
telescope has over an optical???????
Lenses……
• It is a transparent material that bends
or refracts light.
2 main types of lenses;
• Convex: thick in the middle. Bending light
inward. Amount of refraction depends on how
curved the lens is.
• Concaved: thin in the middle. Bends light away
from the lens. (spreads apart)
Top: a convex lens converges light rays
Bottom: a concave lens diverges light rays
Images
• Real image: one that can be projected
onto a screen. The image is upside
down..
• Virtual image: when an object is placed
between a convex lens and its focal
point producing a larger and upright.
i.e… (magnifying glass)
Space Telescopes
• The Hubble
Telescope was
designed to take
pictures of the
whole universe.
• What major
advantage does
the Hubble have
over ground based
telescopes?????
Pictures from the Hubble Space
Telescope
Doppler Shift (effect)
• Sometimes the black lines in a star’s
spectrum are shifted to the Red or Blue
end of the spectrum.
• These shifts occur because of a change in
the distance between the star and Earth.
• When the distance increases (moving
away) = shifted toward the longer
wavelength (RED).
• When the distance decreases (moving
closer) = shifted toward the shorter
wavelength (BLUE).