Lucky imaging

Images taken with ground-based telescopes are subject to the blurring effect of atmospheric turbulence (seen to the eye as the stars twinkling).

[4] In that work, the full width at half maximum (FWHM) of the blurring was estimated, and used to select exposures.

[8][9] In 2007 astronomers at Caltech and the University of Cambridge announced the first results from a new hybrid lucky imaging and adaptive optics (AO) system.

The telescope, with lucky cam and adaptive optics, pushed it near its theoretical angular resolution, achieving up to 0.025 arc seconds for certain types of viewing.

[10] Compared to space telescopes like the 2.4 m Hubble, the system still has some drawbacks including a narrow field of view for crisp images (typically 10" to 20"), airglow, and electromagnetic frequencies blocked by the atmosphere.

In these periods, lasting a small fraction of a second, the correction given by the AO system is sufficient to give excellent resolution with visible light.

This technique is applicable to getting very high resolution images of only relatively small astronomical objects, up to 10 arcseconds in diameter, as it is limited by the precision of the atmospheric turbulence correction.

Being above the atmosphere, the Hubble Space Telescope is not limited by these concerns and so is capable of much wider-field high-resolution imaging.

[13] The development and availability of electron-multiplying CCDs (EMCCD, also known as LLLCCD, L3CCD, or low-light-level CCD) has allowed the first high-quality lucky imaging of faint objects.

Short exposures avoid blurry images or blowing out highlights, and averaging multiple shots reduces noise.