ao - ForOT Optical Turbulence Forecasts
ao - ForOT Optical Turbulence Forecasts
ao - ForOT Optical Turbulence Forecasts
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SPATIAL POWER SPECTRUM OF WAVEFRONT DISTURBANCES<br />
L 0<br />
l 0<br />
Κ (m -1 )<br />
NOTE: A LOW OUTER SCALE<br />
COMBINED WITH VERY<br />
GOOD SEEING IS A GOOD<br />
THING ESPECIALLY FOR<br />
INTERFEROMETRY<br />
‣ inner scale of turbulence (l 0 ≈ 1 cm)<br />
is of little interest for astronomy<br />
(in contrast to laser propagation)<br />
‣ outer scale of turbulence (L 0 ) is of<br />
major interest for astronomy since:<br />
(i) it has dimensions comparable to<br />
the diameters of Large Telescopes<br />
(D ≈ 8 m for VLTs to 42 m for ELTs)<br />
(ii) it is small compared to the baselines<br />
of <strong>Optical</strong> Interferometers<br />
(e.g. VLTI 200 m ; CHARA 330 m )<br />
‣ L 0 depends on number of factors (like<br />
dome size, landscape, vegetation,<br />
height, telescope structure, radiation<br />
cooling, height)<br />
‣ measured L 0 : La Palma/Hershell 2 m<br />
Sydney/SUSI 5 m<br />
Palomar/PTI 16 m<br />
Paranal 22 m<br />
Mauna Kea 27 - 50 m<br />
OHP/France 14 m<br />
‣ it is quite possible for a site to have<br />
multiple outer scales !!!
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