Atmospheric coherence time measurement by modified Fast Defocus method

Akbari, Lida; Darudi, Ahmad; Shomali, Ramin

doi:10.1016/j.ijleo.2021.166494

Cited by 1 publication

(1 citation statement)

References 19 publications

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“…So, the signal in a DIMM is generated mostly by the wave-front curvature. The mask in a DIMM can contain more than two holes [31]. Alternatively, a full-aperture Shack-Hartmann sensor can be used to measure low-order wave-front distortions and to deduce the seeing; AO systems usually estimate the seeing in this way.…”

Section: Absolute and Differential Tiltsmentioning

confidence: 99%

The Elusive Nature of “Seeing”

Tokovinin

2023

Atmosphere

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Atmospheric image blur, “seeing”, is one of the key parameters that influences the selection of observatory sites and the performance of ground-based telescopes. In this review, the common definition of seeing based on the Kolmogorov turbulence model is recalled. The ability of this model to represent real, non-stationary fluctuations of the air refractive index is discussed. Even in principle, seeing (a model parameter) cannot be measured with arbitrary accuracy; consequently, describing atmospheric blur by a single number, seeing, is a crude approximation. The operating principles of current seeing monitors are outlined. They measure optical effects caused by turbulence, sampling certain regions of spatial and temporal spectrum of atmosphreic optical disturbances, and interpret their statistics in the framework of the standard model. Biases of seeing monitors (measurement noise, propagation, finite exposure time, optical defects, wind shake, etc.) should be quantified and corrected using simulations, while instrument comparison campaigns serve as a check. The elusive nature of seeing follows from its uniqueness (a given measurement cannot be repeated or checked later), its non-stationarity (dependence on time, location, and viewing direction), a substantial role of the highly variable surface layer, and a potential bias caused by the air flow in the immediate vicinity of the seeing monitors. The results of seeing measurements are outside the scope of this review.

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Section: Absolute and Differential Tiltsmentioning

confidence: 99%

The Elusive Nature of “Seeing”

Tokovinin

2023

Atmosphere

View full text Add to dashboard Cite

show abstract

Atmospheric coherence time measurement by modified Fast Defocus method

Cited by 1 publication

References 19 publications

The Elusive Nature of “Seeing”

The Elusive Nature of “Seeing”

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