A, B parameterisation coefficients
constants
structure coefficient of the index of refraction
temperature structure coefficient
adimensional pressure coefficient
D (mirror) diameter
temperature structure function
Fr Froude number
f focal distance
e turbulent kinetic energy
g gravity acceleration
h heat transfer rate
central intensity ratio
turbulence intensity
eddy diffusivity for momentum
eddy diffusivity for temperature
L Monin-Obukhov length
length scale of turbulence along mean flow direction
l inner scale of turbulence
N index of refraction
n frequency
P pressure
Q dissipated power
q heat flux normalised by
surface heat flux
Ra Raleigh number
Re Reynolds number
Ri Richardson number
Fried parameter for seeing
S Strehl ratio
T (mean) temperature
t thickness
U wind or air flow speed
friction velocity
v water vapour pressure
z height
telescope azimuth angle
ratio
zenithal angle of the direction of observation
dissipation rate of kinetic energy
dissipation rate of temperature
thermal diffusivity of air
wave number
light wavelength
similarity scale for quantity i
kinematic viscosity
air density
root mean square of quantity i
wavefront rms error
long exposure angular image size on the sky (generally FWHM)
image size due to natural seeing
rms of high frequency guiding errors
MAIN ACRONYMS USED IN THE TEXT
AAT Anglo-Australian TelescopeCFHT Canadian French Hawaii Telescope
CIR Central Intensity Ratio, a measure of the optical quality of a telescope
DIMM Differential Image Motion Monitor, a special 35-cm telescope for measuring seeing
ESO European Southern Observatory
FWHM Full Width Half Maximum of the point spread function
MMT Multi-Mirror Telescope
M1 Primary mirror of a telescope
M2 Secondary (upper) mirror of a telescope
NTT New Technology Telescope, the newest 3.5-m telescope located at ESO's
La Silla observatory
PSD Position sensing detector
PSF Point Spread Function (light intensity profile)
VLT Very Large Telescope, a 4
8-m telescope project presently under construction