The ASL seeing correlates well to VLT-UT science image quality (messenger-no132-11, June 08). The ASL seeing is computed from contemporaneous DIMM-MASS_LITE data (Sep.2004 to July 2007) as in E-ELT-TRE-222-0215.pdf:
Seeing(ASL) = (0.22 * DIMM5/3 + 0.78 * MASS5/3)3/5
|
Min |
5perc. |
Median |
Average |
95perc. |
Max |
Std. dev |
Samples |
DIMM Seeing (arcsec) |
0.26 |
0.52 |
0.86 |
0.96 |
1.77 |
5.86 |
0.42 |
177904 |
ASL Seeing (arcsec) |
0.18 |
0.32 |
0.57 |
0.64 |
1.18 |
3.46 |
0.28 |
177904 |
UT1 S-H CASS
corr. seeing (arcsec) |
0.28 |
0.40 |
0.63 |
0.67 |
1.04 |
1.89 |
0.19 |
23888 |
Case 1: ASL seeing <= 0.5”
(55940 samples)
Case 2: 0.5” < ASL seeing
<= 1.0”(87351 samples)
Case 3: ASL seeing > 1.0”(17124 samples)
BSL seeing = 0.78 * (DIMM5/3 – MASS5/3)3/5
Case 1: BSL seeing <= 0.5”
(85104 samples)
Case 2: 0.5” < BSL seeing
<= 1.0”(62764 samples)
Case 3: BSL seeing > 1.0”(12547
samples)
Monthly BSL average seeing as
function of the Wind Direction for bad seeing
An earlier study based on microthermal sensor measurements had concluded to a much smaller chare of the first 30m in the total seeing:
Measurement of the microthermal activity and Seeing at Paranal (GSM Campaign, Nice University) during a night presenting variable conditions.
The contribution of the layer 2-21m above ground corresponds to an increase of about 8% of the seeing.