Introduction to Astrophysics
Instructor-
Golam Dastegir Al-Quaderi
Professor
Department of Physics, DU
1
, Telescopes
• Definition: Telescopes are instruments/devices
that are used to observe distant objects by
detecting radiation from those.
• The primary form of radiation coming from
distant objects (in astrophysics distant celestial
bodies) is electromagnetic radiation in different
wavelength ranges.
• The most common and historically the first type
of telescopes used were optical telescopes
detecting visible light.
2
, Telescopes
• Optical Telescopes:
A modern refracting telescope
illustration of a 46 m (150 ft) focal length large Keplerian of 200 mm diameter at the
Telescope built by Johannes Hevelius in 1641 Poznań Observatory
https://en.wikipedia.org/wiki/Refracting_telescope 3
, Telescopes
• Galilean Telescopes:
• Galileo Galilei in 1609 made a telescope with a
biconvex objective and biconcave eyepiece
having 3𝑋 magnification.
Galileo Galilei’s telescopes at Museo Galileo in Florence
https://en.wikipedia.org/wiki/Galileo_Galilei
4
Instructor-
Golam Dastegir Al-Quaderi
Professor
Department of Physics, DU
1
, Telescopes
• Definition: Telescopes are instruments/devices
that are used to observe distant objects by
detecting radiation from those.
• The primary form of radiation coming from
distant objects (in astrophysics distant celestial
bodies) is electromagnetic radiation in different
wavelength ranges.
• The most common and historically the first type
of telescopes used were optical telescopes
detecting visible light.
2
, Telescopes
• Optical Telescopes:
A modern refracting telescope
illustration of a 46 m (150 ft) focal length large Keplerian of 200 mm diameter at the
Telescope built by Johannes Hevelius in 1641 Poznań Observatory
https://en.wikipedia.org/wiki/Refracting_telescope 3
, Telescopes
• Galilean Telescopes:
• Galileo Galilei in 1609 made a telescope with a
biconvex objective and biconcave eyepiece
having 3𝑋 magnification.
Galileo Galilei’s telescopes at Museo Galileo in Florence
https://en.wikipedia.org/wiki/Galileo_Galilei
4
