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Published byRichard Montgomery Modified over 9 years ago
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Super Seeing from the AAT Peter Gillingham 26 th 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 -> 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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~3% 0.4 arcsec PARANAL ~ 3% better than 0.4 arcsec (up to 1995) from DIMM measurements
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Seeing distribution from DIMM at the WHT site, Canary Islands. ~ 10% 0.4 arcsec
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midnight
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DIMM data during daytime, Dome C 21/22 Nov 2003 – Sun’s elevation ~ 17 to 5 to 25 deg. FWHM (arcsec) v local time. (with no correction for Zenith Distance) 18:0021:0000:00 03:0006:00 1.0 0.6 0.8 21 st Nov22 nd Nov 0.2 0.0 0.4
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DIMM data during daytime, Dome C 21/22 Nov 2003 18:0021:0000:00 03:0006:00 1.0 0.6 0.8 21 st Nov22 nd Nov 0.2 0.0 0.4 < 0.4 arcsec, experienced ~ 3% of time at Paranal
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DIMM data during daytime, Dome C 21/22 Nov 2003 18:0021:0000:00 03:0006:00 1.0 0.6 0.8 21 st Nov22 nd Nov 0.2 0.0 0.4 < 0.3 arcsec, experienced ~ 0.3% of time at Paranal
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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 28 th Nov 2003 29 th Nov 2003 FWHM arcsec (not corrected for Zenith angle) v local time. 00:0006:0012:0000:0018:00 00:0006:0012:0000:0018:00
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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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18:0021:0000:00 03:0006:00 1.0 0.6 0.8 0.2 0.0 0.4 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 00:0006:0012:0000:0018:0006:0012:0000:0018:00 1.0 0.8 0.0 0.4 1.2 1.6 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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CT 2 data from SAODAR, for 7 th 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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CT 2 data from SODAR for 21 st 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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Comparison of wind speed from Dome C2 AWS with that at 30 m height from SODAR at Dome C. Wind speed (m/s) from AWS at Dome C2, height ~ 3 m Wind speed (m/s) from SODAR at Dome C, height 30 m
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AWS data from Dome Fuji ~ 77 deg S 3810 m Jun 2003 Sep 2003 Aug 2003 Jul 2003
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Super Seeing from the Antarctic Plateau? Is it now time to remove “?” ? YES !
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