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J. M. Beckers (University of Chicago), Zhong Liu (Yunnan Astronomical Observatory)
A collaborative effort between the Yunnan Observatory (YO) of the Chinese Academy of Science and the National Solar Observatory (NSO) has led to the development of the seeing monitor now being used by the NSO for the site testing for the 4 meter Advanced Technology Solar Telescope (ATST). The ATST seeing monitor contains a solar differential image motion monitor (S-DIMM) modeled after the one used by the YO for the site testing at Fuxian Lake. The S-DIMM results in a determination of the Fried Parameter r0. NSO added a linear array of 6 scintillometers which measure cloud cover, the scintillation index and the spatial co-variance of the solar shadow bands. This array is called the SHABAR = SHAdow BAnd Ranger because of its ability to give the height structure of the atmospheric seeing (see the attached web page).
In February this year we combined the ATST SHABAR with the S-DIMM at the Fuxian Lake site. We describe the results of 5 days of observations in the February 9 to 14 period. In summary they are: (a) the average seeing was 1.6 arcsec in the solar direction, 1.2 arcsec for zenith direction, (b) for half of the time the boundary layer seeing contribution was negligible (<10%), (c) at the times when it was significant the scale height of the refractive index structure constant Cn2 was determined to be 20 meters, (d) at those times the r0 derived from the SHABAR agreed well with that observed with the S-DIMM, and (e) the r0 derived from the SHABAR at times when it is small exceeds that of the S-DIMM. This is almost certainly due to the outer scale of turbulence being around 10 - 30 meters in the free atmosphere at heights 1 km and above.
If you would like more information about this abstract, please follow the link to http://www.nso.noao.edu/atstss/SMEXPA.pdf. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.
The author(s) of this abstract have provided an email address for comments about the abstract: jbeckers@rcnchicago.com
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.