Albedo used in astronomy are the (V-band) geometric albedo (measuring brightness when illumination comes from directly behind the observer) and the Bond albedo (measuring total proportion of electromagnetic energy reflected). Their values can differ significantly, which is a common source of confusion. In detailed studies, the directional reflectance properties of astronomical bodies are often expressed in terms of the five Hapke parameters which semi-empirically describe the variation of albedo with phase angle, including a characterization of the opposition effect of regolith surfaces. The correlation between astronomical (geometric) albedo, absolute magnitude and diameter is: formula_7, where formula_8 is the astronomical albedo, formula_9
Single-scattering albedo other methods of computational electromagnetics. The albedo of particles of shapes which are easily parameterized in non-standard co-ordinate systems may be determined through solutions of Maxwell's equation analogues in such coordinate systems. Scattering albedo equations have yet to be determined in elliptical, torroidal, conical and many others. Derivation and solutions to such equations is a field of ongoing research. Single-scattering albedo Single-scattering albedo is the ratio of scattering efficiency to total extinction efficiency (which is also termed "attenuance", a sum of scattering and absorption). Most often it is defined for small-particle scattering of electromagnetic waves. Single-scattering albedo is unitless, and