This website has been created by the members of the
Lucky Imaging team based within the Institute
of Astronomy and the Cavendish
Astrophysics group of the University of
Cambridge, England, UK in order to provide information about this exciting
new technique, how it works, the present status of our latest results, and some
of our ideas for development of the technique in the future.
**** Latest Results: There are exciting new results on observations
of very low mass binary candidates described here:
Very Low-Mass Binaries and a newly
submitted paper on the techniques and
properties we have discovered with Lucky Imaging.****
Lucky Imaging: General Introduction and Results Summary
A telescope is an instrument that deflects all the rays of
light from a distant star or galaxy to form a sharply defined focused image of
the object. In space, a telescope will produce an image whose resolution is only
limited by the diameter of the telescope and the wavelength of light being
focused. If our telescope is on the ground, however, density fluctuations in the
atmosphere cause the rays of light to be deflected slightly so that the focused
images become slightly fuzzy. The atmospheric fluctuations change fairly
rapidly, on timescales of tens of milliseconds, causing the quality of the
focused image also to change rapidly. By using a high-speed camera we can choose
those images that are least affected by the atmosphere and combine them to give
a much higher resolution image then we would get if we simply added together all
the images irrespective of their quality. By doing this we are selecting those
fortunate moments when the fluctuations in the atmosphere are at the smallest.
This is what we call "Lucky Imaging". Lucky imaging techniques may be used both
for astronomical observations with telescopes and for ground-ground imaging such
as surveillance work with long focus lenses.
Lucky imaging is not a new idea. It was originally suggested by Fried (1978)
and these principles have been used really quite extensively by the amateur
astronomy community who have been able to take very high quality images of
bright objects such as Mars and the other planets. There is more information
about Amateur Lucky Imaging here.
The results of Lucky Imaging can be quite dramatic. The
effects of atmospheric density fluctuations mean that the detail that may be
detected in an image is limited. Using a large diameter telescope will allow one
to gather more light but will not increase the detail in the image once a
certain size has been reached that depends on the atmospheric conditions locally
(and these change from day-to-day), and the wavelength of light used. For
typical atmospheric seeing of about one arc second this limits the maximum
resolution to that obtained in the visible with a telescope of only 10
centimetres in diameter.
With Lucky Imaging we can increase the maximum
resolution we can be achieved from the ground by factors of as much as 5-7. With
the ground based 2.5 metre telescope we can match the resolution obtained by the
2.5 metre Hubble Space Telescope, at a tiny fraction of the cost.
The effect on the image quality obtained is shown below.
pictures are shown of the same region of a globular star cluster M15, taken on
the same telescope within a few minutes of one another. The first
was taken with a conventional high-quality scientific CCD camera while the
second was taken with a high-speed CCD camera with the best 10% of images
selected and combined to produce the image shown. To see the full frame images,