The Statistical Distributions and Evolutions of Seeing Values

[摘要] Extensive series of DIMM and MASS seeing values from thirteen astronomical sites are used to examine the shapes of their statistical distributions and their evolutions with time. At all sites, the distributions of seeing values can be satisfactorily reproduced over densities that span more than four orders of magnitude by random combinations of seeing values from two independent equal-population log-normal seeing components. The seeing varies typically by a factor of 4 throughout a night. At good sites, it reaches sub-half-arc second on 80% of the night. It is most stable when near its modal value where the delays for a 10% change in DIMM seeing average ∼50 minutes. The average delays are ∼25 minutes at the 10thand 90thpercentiles of the distributions. These lifetimes differ by a factor of 4 between the fastest and the slowest seeing sites. The MASS seeing evolves ∼7 times faster than the DIMM seeing. These characteristics make forecasting seeing a tall challenge.

[发布机构] Association of Canadian Universities for Research in Astronomy, Département de Physique, Université de Montreal, CP 6128, Succ. Centre-Ville, Montreal; H3C-3J7, Canada^1

[效力级别] 地球科学

[关键词] Average delay;Log-normal;Modal values;Orders of magnitude;Random combination;Statistical distribution