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Loading contentMeasuring how bright things are and resolving their fine detail — the magnitude system, precision photometry, and the interferometry and adaptive optics that sharpen the view.
Measuring brightness and resolving detail.
Deformable mirrors that flex hundreds of times a second to cancel the blurring of Earth's turbulent atmosphere, giving ground telescopes near space-quality sharpness.
Combining the light of separate telescopes so they act as one much larger instrument, achieving resolution impossible for a single dish. Radio interferometry links antennas across continents; it produced the first images of black-hole shadows.
The precise measurement of the brightness of a star or galaxy, in one or more filters. Photometry over time reveals variable stars, transiting planets, and supernovae; photometry in different colours reveals temperature.
Astronomy's logarithmic, backwards brightness scale, in which smaller numbers are brighter. Apparent magnitude is how bright an object looks; absolute magnitude is how bright it truly is — and the difference gives its distance.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.