TelescopesTelescopes

Images can be formed through reflection (mirror) or refraction (lens).

Reflecting mirror

Optical TelescopesOptical Telescopes

Refracting lens

Optical TelescopesOptical Telescopes

Reflecting and refracting telescopes

Optical TelescopesOptical Telescopes

Modern telescopes are all reflectors (use a mirror):

• Light traveling through lens is refracted differently depending on wavelength.

• Some light traveling through lens is absorbed.

Optical TelescopesOptical Telescopes

Image acquisition: Charge-coupled devices (CCDs) are electronic devices, can be quickly read out and reset.

Optical TelescopesOptical Telescopes

Interferometry:

• Combines information from several widely spread radio telescopes as if it came from a single dish.

Radio AstronomyRadio Astronomy

Infrared radiation can image where visible radiation is blocked; generally can use optical telescope mirrors and lenses.

Other AstronomiesOther Astronomies

Much can be learned from observing the same astronomical object at many wavelengths. Here, the Milky Way.

Other AstronomiesOther Astronomies

Electromagnetic SpectrumElectromagnetic Spectrum

All the types of radiation are shown on the All the types of radiation are shown on the electromagnetic spectrum from long wavelengths electromagnetic spectrum from long wavelengths (radio) to short wavelengths (gamma).(radio) to short wavelengths (gamma).

We can only use our eyes to see a very small We can only use our eyes to see a very small portion of the radiation that is emitted in the portion of the radiation that is emitted in the universe (visible light)universe (visible light)

Electromagnetic SpectrumElectromagnetic Spectrum