Adaptive Optics on the 200-inch Hale Telescope at the Palomar Observatory

Adaptive optics is a technique that allows ground-based telescopes to remove the blurring affects caused by Earth's atmosphere. The image below shows the dramatic improvement gained through the use of adaptive optics. On the left is a blurred image without adaptive optics corrections and on the right the corrections reveal a binary star.

The binary star IW Tau is revealed through adaptive optics. The stars have a 0.3 arc second separation. The images were taken by Chas Beichman and Angelle Tanner of JPL.

To make the corrections light passes through the Hale Telescope's light path and down to the Cassegrain focus where the adaptive optics instrument and the PHARO (Palomar High Angular Resolution Observer) camera is located.

The adaptive optics system uses a star as a calibration source and then deforms a small mirror to correct for distortions caused by the atmosphere. The corrections are made faster than the atmosphere can change -- thousands of times per second.

The technique has been used for a variety of science observations which have included long-term observations of the atmospheric changes of the outer planets, studies of the weather on Saturn’s moon Titan, the hunt for brown dwarfs, and the details of star formation.

Adaptive optics does have its limits. In places where there isn't a natural guide star near the object of interest, the technique cannot generally be used.

By projecting a laser into the sky astronomers can create an artificial laser-guide star for use in adaptive optics wherever they see fit. To do so, they shine a narrow sodium laser beam up through the atmosphere. At an altitude of about 60 miles, the laser beam makes a small amount of sodium gas glow. The reflected glow from the glowing gas serves as the artificial guide star for the adaptive-optics system. The laser beam is too faint to be seen except by observers very close to the telescope, and the guide star it creates is even fainter. It can't be seen with the unaided eye, yet it is bright enough to allow astronomers to make their adaptive-optics corrections.

Click on image to enlarge

Quicktime movie of laser taken on an engineering night from inside the dome
The movie covers almost four hours of time from August, 2008.

Quicktime movie of laser guide-star operations (34 mb) The movie shows three hours of laser guide-star operations from April, 2007.

Watch members of the Palomar day crew install the adaptive optics instrument into the Hale Telescope's Cassegrain cage in this time-lapse movie (~62 mb Quicktime movie).

Watch the installation of the Laser Launch Telescope at prime focus in a time-lapse movie (~27 mb Quicktime movie).

First image from the Palomar Laser Guide-Star AO System shows an uncorrected star on the left and the corrected adaptive optics image of the same star on the right.

Adaptive Optics images and information from Palomar Observatory:

  • Robo-AO - a robotic laser guide star adaptive optics system for the Palomar 60-inch telescope
  • Exoplanets HR 8799 B, C, & D
  • Alcor A and Alcor B
  • Adaptive optics images of the LCROSS lunar impact
  • Photos of the Laser guide-star program in action
  • Instrument to reveal hidden worlds by blocking out starlight and The Lyot Project
  • LuckyCam Adaptive Optics
  • The Red Square
  • Neptune and Neptune Rotating
  • Uranus rotation
  • Adaptive Optics observations of the Deep Impact event
  • Jupiter
  • Saturn's moon Titan - coming soon.
  • M 26

  • Laser Guide Star Press Release

  • JPL's Palomar Adaptive Optics Page

  • PALM-3000
  • Project 1640
  • Oxford SWIFT