The Database is part of the ForOT activity and aims to be a tool of
investigation for us and a mean to keep the Large Binocular Telescope
(LBT)
Consortium informed about progress achieved on turbulence
characterization above Mt. Graham (site of LBT). The web page is
conceived to be in constant evolution. The number of measurements
related to the different Astronomical Sites are not homogeneous and not
equivalent
from a statistical point of view. This means that statistic estimators
(cumulative distributions, median and means values) are a function of
sample of measurements emploied.
It is our intention to
try to actualize figure of merit up-dating results using data-set
related to forthcoming
site testing campaigns.

To respect the data usage policies of colleagues who provided us
measurements obtained so far in different astronomical sites this web
page is, at present time,
password protected. On the table are indicated links either to
published papers or analysis unique to these pages.

Content of this page:

- Tabulated summary of OT measurement data
- Definition of terminology used in the table
- Definition of calculations for astro-climatic parameters used throughout these pages
- Cumulative histograms of seeing and isoplanatic angle of the free-atmosphere for 5 astronomical sites

Site of the Measurements | Instrument Type* | Sampling Statistics #/each/total** |
Analysis | Notes | |||
---|---|---|---|---|---|---|---|

external links | internal links | ||||||

Mt. Graham VATT: 32.7 N, 109.87 W; H=3200 |
HVRGS | 851 / 30 sec / 1 eqv.nghts | Egner
& Masciadri, (2007), PASP & ForOT Activity |
GS on the Lennon telescope (VATT) is 35 meters below and 250 meters laterally from the LBT primary mirrors. | |||

GS | 10522 / 50 sec / 8 eqv.nghts | Egner,
Masciadri, McKenna, (2007), PASP (first 16 nights) & ForOT Activity |
free-seeing comparison | ||||

Dome C, AASTINO: 75 06 S, 123 21 E; H=3260 m |
SODAR-MASS | 1701 / 65 sec / 3 eqv.nghts | Lawrence et al.(2004) Nature | Kenyon et al.(2006) PASP | The SODAR data provided are only one J(h_GL) value matching each MASS measurement. | ||

Cerro Pachon: 30 24 S, 70 44 W,; H= 2738 m |
MASS | 40630 / 70 sec / 64 eqv.nghts | Tokovinin
and Travouillon (2006) MNRAS (only calibrated measurements) |
seasonal trends | There are DIMM measurements from a combined MASS-DIMM instrument, but they are not provided. Of those available, the newer data are from a 6 meter tower, older data are from a 1.5 meter tripod. | ||

Cerro Tololo: 30 09 S, 70 48 W; H=2215 meters |
MASS | 129153 / 70 sec / 206 eqv.nghts | |||||

Mauna Kea: 19 49 N, 155 28 W; H=4200 M |
MASS | 3819 / 65 sec / 6 eqv.nghts | Tokovinin
et al.(2005) PASP (4 nights) |
Generalized MASS using the U of Hawaii 24 inch telescope. 1369 of these measurements are strongly affected by errors from tracking and saturation of the signal due to strong free-seeing. | |||

DIMM | ~3819 / | 0.25 meter Meade on the coude roof of the U of Hawaii 88 inch telescope. There was another DIMM instrument running simultaneously on a tripod outside the U of Hawaii 24 inch, but it is contaminated by too much surface turbulence. | |||||

GS | 6530 / | Generalized SCIDAR with the U of Hawaii 88 inch telescope | |||||

Cerro Paranal 70 24' W, 24 37' S; H=2400 m |
MASSLite | ||||||

DIMM | http://www.eso.org/gen-fac/pubs/astclim/paranal/asm/mass/MASS-LITE/Paranal/ |

- *
- GS = G-SCIDAR = Generalized Scintillation Detection And Ranging
- HVRGS = High Vertical Resolution GS
- MASS = Multiple Aperture Scintillation Sensor
- DIMM = Dual Image Motion Monitor
- SODAR = Sonic Detection And Ranging
- **
- Number of Samples / typical sample interval (seconds) / total length of intervals shorter than 180 sec
- eqv.nghts = equivalent number of nights is the length of time in units of 12 hours.

In the following plot we provide cumulative histograms
of isoplanatic angle and seeing from the free atmosphere, defined here
to be the above 700 meters from the site. Isoplanatic angle and seeing
are common astro-climatic parameters defined as

,

.

Unless stated otherwise the wavelength λ is 0.5 microns in these pages.
The Cn2 moment μ with subscript m is computed from N layers of Cn2
integrals Ji

.

The hi is vertical height above the site of the ith Cn2 integral.
Ideally we would measure an arbitrarily large number of Cn2 integrals.
Each method of OT measurment has its own limitations that limit the
number N. In general the layer measurements can be modeled with

,

where Wi is some weighting function for the ith layer. The height hi is
generally defined to be at the peak of Wi.

The plot below shows cumulative histograms of the above
astro-climatic parameters calculated for five of the astronomic sites
in the
above table. These pictures are for
internal use ONLY.

Fig. 1 - Caption: Raw data set for the astronomical sites are related to:

Mt. Graham: All nights (37 at present)

Mauna Kea: Tokovinin et al. 2005, PASP, 117, 395

Dome C: Lawrence et al., 2004, Nature, 431, 278

Cerrto Tololo and Cerro Pachon: http://139.229.11.21/massindex.php?Submit2=MASS+Database

Samples:

Mount Graham: 20/05/2005 - 29/10/2007 (SCIDAR, 100 hours)

Dome C: 24/03/2004 - 05/04/2004 (MASS, 30 hours)

Cerro Pachon: 09/01/2003 - 20/11/2006 (MASS, 760 hours)

Cerro Tololo: 19/03/2002 - 04/12/2006 (MASS, 2400 hours)

Mauna Kea: 19/10/2002 - 24/10/2002 (MASS, 70 hours)

WARNING: We invite the reader to not retrieve fast and wrong conclusions on the quality of the different sites. As it is known, the cumulative distributions are quite sensitive to the sample emploied. Here down the same cumulative distribution of Fig. 1 is calculated using only the first 16 nights of Mt. Graham (instead of 32 nights as Fig. 1). The reader can note that the statistic of the distribution changed in a not negligible way.

Fig. 2 - Caption: Same as Fig.1 but with a different statistic sample of nights

Data are treated by Jeff Stoesz

E.Masciadri, 1/2008