LuckyCam + AO at Palomar

This page details results from the new combined Lucky Imaging and Adaptive Optics instrument at Palomar observatory. The system was recently named one of Time Magazine's Best Inventions of 2007.

Image gallery

How it works

A direct comparison with the Hubble Space Telescope

The team

Images of the instrument

Links

The new LAMP (LuckyCam) instrument at Palomar combines two telescope image-improvement technologies to obtain the highest-resolution direct images of space ever recorded in visible light.

Adaptive Optics has been used for several years to obtain diffraction-limited results in the near-infrared, but has not up to now been used in the visible on 5m+ telescopes. Lucky Imaging has been used with visible light on 2.5m telescopes. Using both together we obtained the first routine diffraction-limited imaging with visible light on telescopes as large as 5m, twice the diameter of the Hubble Space Telescope. The project is primarily a collaboration of Caltech and the University of Cambridge.

The new system is useful for a wide variety of astronomical research, including high-resolution imaging of nebulae (where visible light emission traces particular elements) and projects which require exquisite angular resolution to detect stars very close to each other. In some images the system produces twice the resolution of the Hubble Space Telescope. However, the atmosphere limits the maximum image size to be about 10X smaller than the Hubble Space Telescope's.

Please contact Nicholas Law (the principal investigator of this project, nlaw at astro.caltech.edu), or Craig Mackay (the leader of the LuckyCam team, cdm at ast.cam.ac.uk), for further information.

A field of stars from the core of the M13 globular cluster taken with the new instrument. The same field taken with the Hubble Space Telescope


Image Gallery

Cat's Eye Nebula

These images show the improvements compared to standard ground-based imaging methods, but do not show the full potential of our new system. Please see the below images of the M13 globular cluster for a comparison with the Hubble Space Telescope.

Example image of a binary star

Taken at 710nm (just red of visible light) in fairly standard conditions. A standard instrument on a telescope on the ground would not be able to separate these two stars. The grid pattern behind the bright star is due to residual "waffle" errors resulting from correcting the turbulence.


The core of the M13 globular cluster

Colour image taken with 770nm and 900nm light.
The "1 arcsec" scale bar is the size of a typical star taken on a standard ground-based instrument - the resolution gain from the Lucky Imaging and Adaptive Optics combination is rather pleasing! Many more stars are visible than would normally be possible.

How it works

Until now, images from ground-based telescopes have been invariably blurred by Earth's atmosphere. Astronomers have developed a technique, known as adaptive optics (AO), to correct the blurring, but so far it has only worked successfully in the infrared, where the smearing is greatly reduced. However, a new noise-free, high-speed camera has been developed at the Institute of Astronomy in Cambridge that, when used behind the infrared Palomar Adaptive Optics System, at last makes very high resolution imaging possible in ordinary visible light using large telescopes.

The camera works by recording partially corrected adaptive optics images at high speed (20 frames per second or more). Software then checks each image to sort out which are the sharpest. Many are still significantly smeared by the atmosphere, but a small percentage of them are unaffected. These are combined to produce the final high-resolution image that astronomers want. The technique is called "Lucky Imaging" because it depends on the chance fluctuations in the atmosphere sorting themselves out and providing a set of images that is easier for the adaptive optics system to correct.


The Team

The instrument was a collaboration of Caltech and Cambridge University. The team was led by Nicholas Law, who also produced the final images at Caltech. The camera hardware, including the new ultra-low-noise photon-counting camera, was designed and built by Craig Mackay at the University of Cambridge. Mike Ireland, Anna Moore and Rich Dekany assisted in the project at Caltech.

We used Caltech's famous Hale Telescope and its adaptive optics system.


Comparison of our results with the Hubble Space Telescope and a standard ground-based instrument (scroll right)

LuckyCam + AO, 770nm (SDSS i'), 0.6 arcsec seeing.

50 second exposure (10% selection from 500 seconds). Strehl ~0.1. LuckyCam's resolution is best towards the middle-bottom of the frame (near the guide star). To guide the eye a red box shows a region where the resolution increase is particularly easy to see, also shown above.

HST ACS 660nm 90-second exposure (drizzled, calibrated)

LuckyCam + AO PSFs have large halos around the stars but the star cores are 2X more compact than HST. The stars in the red box are clearly more easily separated with LuckyCam than HST.

Standard ground-based instrument

The same field without LuckyCam and Adaptive Optics - what a standard instrument would see. 10 arcsec FOV, 0.6 arcsec seeing.


Pictures of LuckyCam attached to the Palomar Hale Telescope and its Adaptive Optics System

Click for larger versions (1.5MB or so)

A CAD model of the instrument. The adaptive optics system is not shown. Light from the telescope comes from the right side of the instrument; the detector is the large box in the middle.
LuckyCam (LAMP) is the small bright rectangular cage visible in the open door to the larger cage. Its covers are open and wiring and other equipment is visible.
A close-up of LuckyCam with its covers on.

Links

Lucky Imaging website at the University of Cambridge. Conventional lucky imaging and some more details on the system described here: http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/

Palomar Adaptive Optics: http://www.astro.caltech.edu/palomar/AO/

Palomar observatory: http://www.astro.caltech.edu/palomar/

Wikipedia page: http://en.wikipedia.org/wiki/Lucky_imaging