Ch 06-01 Basic Properties of Optical Telescopes
- Refractors
- light-gathering power
~ D2
- magnifying power
~ fobj / feye
(Check the image size on the focal plane.)
- surface brightness
~ D2feye2
/ fobj2
(The F-value is F = fobj / D)
chromatic aberration
Reflectors
- spherical aberration
- various designs
Newtonian, Cassegrain, Schmidt-Cassegrain, Maksutov-Cassegrain, ...
Ritchey-Chretien telescopes (RCT): hyperbolic primary and secondary mirrors, most often used in research-class telescopes
Examples of RCT
The 10.4 m Gran Telescopio Canarias at Roque de los Muchachos Observatory
The two 10 m telescopes of the Keck Observatory
The four 8.2 m telescopes comprising the Very Large Telescope in Chile
The 8.2 m Subaru telescope at Mauna Kea Observatory
The two 8 m telescopes comprising the Gemini Observatory
The 4.1 m Visible and Infrared Survey Telescope for Astronomy at the Paranal Observatory (Chile)
The 3.5 m Calar Alto Observatory telescope at mount Calar Alto (Spain)
The 3.5 m Herschel Space Observatory currently operating in orbit at the L2 point 1.5 million km from Earth
The 3.5 m WIYN Observatory at Kitt Peak National Observatory
The 2.5 m Sloan Digital Sky Survey telescope (modified design) at Apache Point Observatory, New Mexico, U.S.A.
The 2.4 m Hubble Space Telescope currently in orbit around the Earth
The 2.2 m Calar Alto Observatory telescope at mount Calar Alto (Spain)
The 2.1 m San Pedro Martir Observatory telescope at Baja California (Mexico)
The 2 m telescope at Rozhen Observatory
The 2 m Himalayan Chandra Telescope of the Indian Astronomical Observatory, Hanle, India
The 1.8 m Pan-STARRS telescopes at Haleakala on Maui, Hawaii
The 85 cm Spitzer Space Telescope, infrared space telescope currently operating in Earth-trailing orbit
Mounting
Alt-azimuthal vs Equatorial
German type vs Fork type
Resolving power (angular resolution)
- Angular radius of a diffraction disk
α = 1.22 λ/D (radian)
= 2.5 x 105 λ/D (arcsec)
for λ = 6000 Å, α = 1.5" /(D/10cm)
- Due to turbulence in the atmosphere, a seeing disk is typically
about larger
than 1". Under a very good condition, like on top of Mauna Kea, it could be
about 0.5".
- Adaptive optics
[ESO AO technology],
[ESO AO for the public],
[The ATNF AO site]
- Astronomical optical/infrared interferometry, in progress.