high-resolution imaging

The phrase high-resolution imaging is used in astronomy, generally meaning "better angular resolution than what we normally get", the actual resolution-range intended varying according to the subfield's usual practice and tools. The highest resolution is generally achieved using interferometry with the longest baselines combined with the shortest wavelengths, i.e., very-long-baseline interferometry with millimeter waves, such as the Event Horizon Telescope, for which 60-micro-arcsecond resolution has been cited. Short of that, ALMA's utility is its efficient production of high-resolution images, producing images with resolutions up to roughly a milliarcsecond. For the future, sub-micro-arcsecond resolution is now a general goal within astronomy.

Increasing resolution without use of interferometry is generally achieved through larger apertures (a motivation for the current major extremely large telescope projects), with speckle suppression techniques including PSF fitting, lucky imaging, and adaptive optics, with space telescopes to escape seeing issues, and with interferometry, as above as well as including space telescopes to create even longer baselines, and with optical interferometry. Specialized techniques have also been considered, and in some cases used, for very high resolution, one general notion being the use of astronomical objects to assist in viewing others, including:

• gravitational lensing.
• occultation observations, including using diffraction patterns associated with the beginning and end of an occultation, as well as timing.
• refraction by astronomical objects, including atmospheres, and clouds, e.g., using scintillometry.
• Earth atmosphere, such as methods of using Cherenkov telescopes and methods analyzing air showers.