TelescopesOctober 31

Telescope Design• There are two types of optical

telescopes –Reflecting-uses a curved mirror

to gather and concentrate a beam of light–Refracting-uses lens instead of

a mirror to focus incoming light

Refraction telescopes• The objective in a refracting

telescope refracts or bends light.This refraction causes parallel light rays to converge at a focal point; while those which were not parallel converge upon a focal plane.

Refraction Telescopes

Types of Reflection Telescopes

•Newtonian•Cassegrain

Newtonian Telescopes• Newtonian telescope-light is

intercepted before it reaches the prime focus, and then deflected by 90 degrees• Smaller design, preferred by

amateur astronomers

Cassegrain Telescopes• The Cassegrain reflector is

a combination of a primary concave mirror and a secondary convex mirror

Reflection Telescope

Hubble Telescope•Hubble works on the same principle as the first reflecting telescope built in the 1600’s by Isaac Newton.

Hubble Telescope• Light enters the telescope

and strikes a concave primary mirror, which acts like a lens to focus the light. The bigger the mirror, the better the image.

Hubble Telescope• In Hubble, light from the primary

mirror is reflected to a smaller secondary mirror in front of the primary mirror, then back through a hole in the primary to instruments clustered behind the focal plane (where the image is in focus).

Mirror Size on Hubble Telescope

•Primary mirror-2.4 meters (94.5 inches) in diameterSecondary mirror-0.3 meters (12 inches) in diameter

Angular resolution• Hubble's angular resolution is

0.05 arcsecond. This is the "sharpness" of Hubble's vision. If you could see as well as Hubble, you could stand in New York City and distinguish two fireflies, 1 m (3.3 feet) apart, in San Francisco

Facts about Hubble Telescope

• Hubble weighs 24,500 pounds -- as much as two full-grown elephants.• During its lifetime Hubble has made

about 800,000 observations and snapped about 500,000 images of more than 25,000 celestial objects

Chandra X-Ray Observatory

• Launched on July 23, 1999• This is an X-Ray Telescope• Designed to observe X-rays

from high-energy regions of the universe, such as the remnants of exploded stars

Comparison of Crab Nebula

Tracking Chandra• The Space Shuttle Columbia delivered

Chandra to a low Earth orbit. Then, the Inertial Upper Stage rocket boosted Chandra up to a higher altitude where a built-in propulsion system took Chandra to its final orbit. This elliptical orbit takes the spacecraft to an altitude of 133,000 km - more than a third of the distance to the moon - before returning to its closest approach to the Earth of 16,000 kilometers

Chandra’s Orbit

• It takes approximately 64 hours and 18 minutes to complete an orbit.

Vision, Hope, and Triumph: Hubble Telescope

• http://www.nasa.gov/multimedia/nasatv/on_demand_video.html?param=http://anon.nasa-global.edgesuite.net/anon.nasa-global/ccvideos/GSFC_20081009_VisHopeTri.asx&_id=168629&_title=Vision%2C%20Hope%2C%20Triumph%3A%20The%20Hubble%20Space%20Telescope&_tnimage=281