Where does aberration collide?

The small apparent change in a star's position caused by the combination of the observer's motion through space and the finite speed of light: as Earth travels along its orbit, starlight appears to arrive from a slightly shifted direction, tracing a tiny yearly ellipse on the sky. James Bradley's 1728 report to the Royal Society, An account of a new discovered motion of the fix'd stars, first identified and named this effect while he was searching for stellar parallax. The referent is an apparent angular displacement set by relative velocity, not a flaw in a lens, a psychological rating, or a property of an experimental design.[1]

Unit

One angle of apparent displacement, in arcseconds

Recovery means

Not applicable

Measured by

Determined from precise positional astronomy across the year, giving a maximum yearly shift near 20.5 arcseconds

A departure of a real optical system from perfect imaging, so that rays leaving one point of an object fail to meet again at a single sharp point and the image is blurred or misshapen. Ludwig Seidel's 1856 paper Zur Dioptrik, in Astronomische Nachrichten, derived the third-order theory that separates these defects into five distinct types, now called the Seidel aberrations. The referent is an imaging error built into a lens or mirror, unrelated to the apparent motion of starlight, a schizotypy measure, or a criterion for choosing a fractional design.[2]

Unit

One departure of the wavefront from the ideal, scaled by aberration coefficients

Recovery means

Not applicable

Measured by

Quantified by wavefront error or ray-traced spot size, and decomposed into Seidel or Zernike coefficients

In psychopathology research, a self-reported distortion in how a person perceives their own body or immediate surroundings, treated as a marker of proneness to psychosis. Loren Chapman, Jean Chapman, and Michael Raulin's 1978 study Body-image aberration in schizophrenia introduced questionnaire scales that measure these reported distortions, later used widely to identify schizotypy in nonclinical samples. The referent is a measured psychological trait recorded on a rating scale, not an apparent stellar motion, a lens defect, or a design criterion.[3]

Unit

One respondent's score on a true/false perceptual aberration scale

Recovery means

Not applicable

Measured by

Assessed by summing endorsed items on the Perceptual Aberration Scale, a self-report questionnaire

In the design of experiments, a rule for choosing among fractional factorial designs by minimizing how much low-order effects are confounded, or aliased, with one another. Arthur Fries and William Hunter's 1980 paper on minimum aberration designs, in Technometrics, defined the criterion, which ranks designs by the pattern of shortest confounded effect strings and prefers the one with the fewest at the lowest order. The referent is a numeric property of an experimental plan, not the apparent motion of a star, an imaging defect, or a psychological rating.[4]

Unit

One design's aberration, from its word-length pattern of confounded effects

Recovery means

Not applicable

Measured by

Computed from the design's defining relation as the word-length pattern, then minimized to rank candidate designs