5: Telescope and Observing
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He burned his house down for the fire insurance
And spent the proceeds on a telescope
To satisfy a lifelong curiosity
About our place among the infinities
The strongest thing that’s given us to see with’s
A telescope. Someone in every town
Seems to me owes it to the town to keep one.
In Littleton it may as well be me.
Robert Frost
The Star-Splitter
This module introduces you to the primary instrument used by astronomers: the telescope, as well as how the telescope works. From its historical first use to today’s modern instruments, the telescope changed forever how we look at our Universe.
Upon completion of this module, the student will be able to:
- Identify the types of telescopes and telescope mounts
- Describe the differences between the refracting telescope and reflecting telescope, including both positive and negative features
- Describe the types of instruments astronomers use with the telescope and the function of each type
- Explain why space-based telescopes are of such importance to today’s astronomers and the collection of information
- 5.1: The Telescope
- This page details the history and role of early spectacle makers, akin to modern optometrists in aiding vision correction. It then explores telescopes, emphasizing their function to collect and magnify light for enhanced detail resolution, with larger sizes typically offering better clarity barring atmospheric limitations.
- 5.2: Early Telescopes
- This page discusses Jan Lipperhey, who invented the first refracting telescope in 1608 but did not patent it, leading to uncertainty about the true inventor. Galileo Galilei enhanced Lipperhey's design in 1609, creating a more powerful telescope that facilitated crucial astronomical discoveries and supported the heliocentric model of the universe.
- 5.3: Telescopic Observations
- This page discusses Galileo's observations of Jupiter and its Galilean Satellites, as well as Sir Isaac Newton's construction of the first Reflecting Telescope in 1668, which utilized a concave mirror for light focus, inspired by Galileo's ideas.
- 5.4: Telescope Optical Types
- This page discusses various types of telescopes categorized by their optical systems: refracting telescopes use lenses, reflecting telescopes utilize concave mirrors, and compound telescopes combine both. It also highlights specialized telescopes for specific electromagnetic wavelengths. Additionally, binoculars are mentioned as compact refractors, while variations such as Newtonian reflectors are noted to show different designs and uses in reflecting telescopes.
- 5.5: Telescope Mounts
- This page discusses telescope mounts, which support two main types: alt-azimuth and equatorial. Alt-azimuth mounts provide movement in horizontal and vertical directions, while equatorial mounts align with Earth's axis for star tracking. Additionally, Go-To telescope mounts use technology such as microprocessors and GPS to automatically locate celestial objects, enhancing the astronomical experience.
- 5.6: Images from the Telescope
- This page explains that telescope images can be viewed using the eye or captured with film, digital cameras, or CCDs for astrophotography. It also discusses the use of a spectroscope to analyze light by breaking it into wavelengths (spectroscopy) and mentions a photometer for measuring light intensity.
- 5.7: Space-Based Telescopes
- This page discusses the Hubble Space Telescope's capabilities for clear space observations and mentions the upcoming launch of the Webb Space Telescope by NASA in 2018. It also highlights the role of various planetary probes, orbiters, and rovers in studying celestial bodies, along with the focusing of some telescopes on specific wavelengths like Infrared, Ultraviolet, Gamma, and Cosmic rays.
- 5.8: Light Pollution
- This page discusses the challenges of light pollution on Earth-based telescopes, affecting visibility of celestial objects and disrupting ecosystems. It highlights financial implications and suggests solutions like shielded lighting, efficient sodium vapor lamps, and advancements in LED technologies to mitigate the issue.
- 5.9: Space-based Telescope
- This page outlines the history of the space-based telescope concept, originating with Hermann Oberth in 1923 and further advanced by Lyman Spitzer in 1946. It describes the evolution of the Large Space Telescope idea, which gained Congressional funding in 1978 and was ultimately named the Hubble Space Telescope (HST) in honor of Edwin Hubble. The HST was successfully launched on April 24, 1990, after overcoming various design, construction, and flight delays linked to the Challenger disaster.
- 5.10: Hubble Space Telescope
- This page discusses the Hubble Space Telescope's early issues with its primary mirror, which affected its focus. A successful corrective optics installation by astronauts in December 1993 resolved these problems, resulting in breathtaking images that have gained widespread admiration from astronomers and the public.