Telescopes



Topic 11 – Exploring the Solar System
11.14 - Know that the human eye is limited in astronomical observations by its small aperture and limited sensitivity in low light

11.15 - Understand how the objective element of a telescope captures and focuses light so that the image can be magnified by an eyepiece

11.16 - Know that convex (converging) lenses and concave (converging) mirrors can be used to collect and focus light from astronomical objects

11.17 - Understand how simple telescopes can be made by combining an objective (lens or mirror) with an eyepiece

11.18 - Understand the basic design of the following in terms of their key elements:
a) Galilean refracting telescope
b) Keplerian refracting telescope
c) Newtonian reflecting telescope
d) Cassegrain reflecting telescope
(detailed ray diagrams not required)

11.19 - Understand that the ‘light grasp’ of a telescope is directly proportional to the area of the objective element and thus the square of the diameter of the objective element

11.20 - Know that the aperture of a telescope is related to the diameter of the objective element

11.21 - Know that the field of view is the circle of sky visible through the eyepiece, measured in degrees or arcmin

11.22 - Understand the resolution of a telescope is:
a) proportional to the diameter of the objective element
b) reduced by observing at a longer wavelength

11.23 - Be able to use the formula for the magnification of a telescope:
fo = magnification
fe
where fo is the focal length of the objective element and fe is the focal length of the eyepiece



11.24 - Understand the importance of Galileo's early telescopic observations in establishing a heliocentric (Sun-centred) model of the Solar System

Topic 13 – Exploring starlight

13.20 - Know that most modern astronomical observations are recorded using digital sensors that convert light into electrical signals, which can then be processed and stored as data files

13.21 - Understand how astronomers obtain and study the patterns of spectral lines in the light from astronomical objects

13.22 - Know that the Earth’s atmosphere blocks almost all of the radiation of different wavelengths in the electromagnetic spectrum, except visible light and radio waves

13.23 - Know that only optical and radio telescopes should be located at sea level on the Earth’s surface

13.24 - Understand how a simple radio telescope operates

13.25 - Understand why radio telescopes need extremely large apertures in order to maintain a useful resolution

13.26 - Understand how multiple radio telescopes can operate as an aperture synthesis system (array)

13.27 - Know that radio astronomy has been important in the discovery of quasars, jets from black holes, the structure of the Milky Way and protoplanetary discs

13.28 - Understand why some infrared telescopes can operate in high-altitude locations, on the Earth's surface

13.29 - Know that infrared astronomy has been important in the discovery of protostars, dust and molecular clouds and hotspots on moons

13.30 - Understand the detrimental effect of the Earth's atmosphere on the quality of images formed by telescopes on the Earth’s surface

13.31 - Understand why telescopes operating outside the optical and radio ‘windows’ need to be sited above the Earth’s atmosphere

13.32 - Understand the advantages and disadvantages of space telescopes and detectors, including orbital observing platforms

13.33 - Understand how gamma ray, x-ray and ultraviolet astronomy have been important in the discovery of gamma ray bursts, black hole accretion discs and the corona and chromosphere structure of young stars

13.34 - Understand how a telescope alters the appearance of:
a) stars
b) double stars
c) binary stars
d) open clusters
e) globular clusters
f) nebulae
g) galaxies

 

In this section you will learn about different types of telescope, how they work and useful terms.

Some terminology you will read in this section:

  • Objective: The mirror or lens of a telescope
  • Primary: The main objective
  • Secondary: Usually a smaller eyepiece

 

WARNING

Never look directly at the Sun with a telescope or binoculars