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Super Seeing from the AAT

Super Seeing from the AAT. Peter Gillingham 26 th March 2003. 1991 Herstmonceux Conference: “ Super Seeing from the AAT ? ” (Australian Antarctic Territory)

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Super Seeing from the AAT

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  1. Super Seeing from the AAT Peter Gillingham 26th March 2003

  2. 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.

  3. from DIMM measurements ~3% 0.4 arcsec PARANAL ~ 3% better than 0.4 arcsec (up to 1995)

  4. Seeing distribution from DIMM at the WHT site, Canary Islands. ~ 10% 0.4 arcsec

  5. midnight

  6. 1.0 0.8 0.6 0.4 0.2 0.0 18:00 21:00 00:00 03:00 06:00 21st Nov 22nd Nov FWHM (arcsec) v local time. (with no correction for Zenith Distance) DIMM data during daytime, Dome C 21/22 Nov 2003 – Sun’s elevation ~ 17 to 5 to 25 deg.

  7. 1.0 0.8 0.6 0.4 0.2 0.0 18:00 21:00 00:00 03:00 06:00 21st Nov 22nd Nov < 0.4 arcsec, experienced ~ 3% of time at Paranal DIMM data during daytime, Dome C 21/22 Nov 2003

  8. 1.0 0.8 0.6 0.4 0.2 0.0 18:00 21:00 00:00 03:00 06:00 21st Nov 22nd Nov < 0.3 arcsec, experienced ~ 0.3% of time at Paranal DIMM data during daytime, Dome C 21/22 Nov 2003

  9. Best DIMM data so far from Dome C ( in daylight )

  10. 00:00 06:00 12:00 18:00 00:00 DIMM measures during daytime at Dome C 28th Nov 2003 29th Nov 2003 FWHM arcsec (not corrected for Zenith angle) v local time. 00:00 06:00 12:00 18:00 00:00

  11. 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

  12. 1.0 0.8 0.6 0.4 0.2 18:00 21:00 00:00 03:00 06:00 0.0 Comparison of DIMM measures from Dome C with simultaneous AWS measures from Dome C2 21/22 Nov 2003

  13. 2.0 1.6 1.2 1.0 0.8 0.4 0.0 00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00 0.0 Dome C DIMM seeing, arcsec FWHM, Nov 28 and 29 Temperature and wind speed from Dome C2 AWS

  14. Temperature and wind speed record from AWS, Dome C2, Feb 1996

  15. Temperature and wind speed record from AWS, Dome C2, July 1996

  16. 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.

  17. CT2 data from SODAR for 21st June 2003.For 30 out of 41 sets of data, no significant returns at any height.

  18. Number of SODAR data sets each day, out of 41 at 30 min intervals, which gave no significant return at any height

  19. Mean SODAR measures as a function of height, month by month at Dome C in 2003

  20. 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.

  21. AWS data from Dome Fuji ~ 77 deg S 3810 m Jul 2003 Jun 2003 Aug 2003 Sep2003

  22. Super Seeing from the Antarctic Plateau? • Is it now time to remove “?” ? • YES !

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