Super Seeing from the AAT

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Super Seeing from the AAT

• Peter Gillingham
• 26th March 2003

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• 1991 Herstmonceux Conference Super Seeing from
  the AAT ? (Australian Antarctic Territory)
• We believed Antarctic plateau would offer
  extremely good seeing but likely upset by thermal
  mixing in boundary layer, something like 100 m
  deep. High temperature gradient in air near snow
  -gt bad thermal inhomogeneity in even light wind.
  Likely better on plateau domes than at S Pole.
• DIMM and SODAR at S Pole confirmed this. SODAR
  showed boundary layer up to 300m deep while,
  above that, scintillation and balloon thermometry
  indicated 0.2 arcsec.
• Dome C SODAR Feb-June 2003 and DIMM summer 2003/4
  indicate this site much better than South Pole
  and almost certainly better than Mauna Kea or any
  other mid-latitude site.

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from DIMM measurements
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0.4 arcsec
PARANAL 3 better than 0.4 arcsec (up to 1995)
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Seeing distribution from DIMM at the WHT site,
Canary Islands.
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0.4 arcsec
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midnight
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FWHM (arcsec) v local time. (with no correction
for Zenith Distance)
DIMM data during daytime, Dome C 21/22 Nov
2003 Suns elevation 17 to 5 to 25 deg.
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lt 0.4 arcsec, experienced 3 of time at Paranal
DIMM data during daytime, Dome C 21/22 Nov 2003
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lt 0.3 arcsec, experienced 0.3 of time at
Paranal
DIMM data during daytime, Dome C 21/22 Nov 2003
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Best DIMM data so far from Dome C ( in daylight
)
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DIMM measures during daytime at Dome C
28th Nov 2003
29th Nov 2003
FWHM arcsec (not corrected for Zenith angle) v
local time.
0000
0600
1200
0000
1800
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Temperature and wind speed data from Automated
Weather Station at Dome C2. Nov. 2003. ( 3 metre
above snow 70 km from Dome C )
Periods in which DIMM measures were recorded
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Comparison of DIMM measures from Dome C with
simultaneous AWS measures from Dome C2 21/22 Nov
2003
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2.0
0.0
Dome C DIMM seeing, arcsec FWHM, Nov 28 and 29
Temperature and wind speed from Dome C2 AWS
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Temperature and wind speed record from AWS, Dome
C2, Feb 1996
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Temperature and wind speed record from AWS, Dome
C2, July 1996
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CT2 data from SAODAR, for 7th Feb., 2003, at 30
min intervals. Note build-up of returns when
Sun was high. For 24 out of 41 sets of data, no
significant returns at any height from 30 to 900
metres.
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CT2 data from SODAR for 21st June 2003. For 30
out of 41 sets of data, no significant returns at
any height.
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Number of SODAR data sets each day, out of 41 at
30 min intervals, which gave no significant
return at any height
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Mean SODAR measures as a function of height,
month by month at Dome C in 2003
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Wind speed (m/s) from AWS at Dome C2, height 3 m
Wind speed (m/s) from SODAR at Dome C, height 30 m
Comparison of wind speed from Dome C2 AWS with
that at 30 m height from SODAR at Dome C.
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AWS data from Dome Fuji 77 deg S 3810 m
Jul 2003
Jun 2003
Aug 2003
Sep2003
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• Super Seeing from the Antarctic Plateau?
• Is it now time to remove ? ?
• YES !