Solar Site Survey for the Advanced Technology Solar Telescope. I. Analysis of the Seeing Data

Abstract

ABSTRACT. The site survey for the Advanced Technology Solar Telescope concluded recently after more than 2 years of data gathering and analysis. Six locations, including lake, island, and continental sites, were thoroughly probed for image quality and sky brightness. The present paper describes the analysis methodology employed to determine the height stratification of the atmospheric turbulence. This information is crucial, because daytime seeing is often very different between the actual telescope aperture (∼30 m) and the ground. Two independent inversion codes have been developed to simultaneously analyze data from a scintillometer array and a solar differential image monitor. We show here the results of applying them to a sample subset of data from 2003 May that was used for testing. Both codes retrieve a similar seeing stratification through the height range of interest. A quantitative comparison between our analysis procedure and actual in situ measurements confirms the validity of the inversions. The sample data presented in this paper reveal a qualitatively different behavior for the lake sites (dominated by high-altitude seeing) and the rest (dominated by near-ground turbulence).

The Big Bear Solar Observatory Ca II K‐line index for solar cycle 23

“…After refurbishing, it was 0.15 nm and the contrast of the Ca II K filtergrams had to be reduced by factor of 0.65 to correct for the higher contrast values now measured in the inner line core of the Ca II K-line, i.e., the contrasts levels reported in this paper have been adapted to the wider bandpass and are used to allow a better comparison with the original Ca II K indices. The total of 2634 Ca II K-line filtergrams included in this analysis corresponds to a 73.5% coverage of the observing period from 1996 January 1 to 2005 www.an-journal.org October 24, which is an excellent value for a single observing station and is in good agreement with the clear time fraction of the Advanced Technology Solar Telescope (ATST) site survey (see Hill et al 2004Hill et al , 2006Socas-Navarro et al 2005;Verdoni & Denker 2007). The quality of the BBSO Ca II K-line images benefits from the good and stable seeing conditions at this lake-site observatory.…”

Solar Ground-Layer Adaptive Optics

“…In addition to using several discrete guide stars for wave-front sensing, our wavefront approaches can also use the entire sunspot for wavefront sensing, which provides a unique solution for sunspot high-resolution imaging that other systems cannot offer. Our past experiences (Ren & Dong 2012;Ren & Zhu 2013;Ren et al 2014b) with sunspot wavefront sensing technique indicates that such a S-GLAO system with the proposed wavefront sensing approaches will be able to deliver extremely stable wavefront corrections at different seeing conditions, including the extreme bad seeing conditions with the Kitt Peak NSO 1.6-m McMP telescope where the typical daytime seeing parameter r 0 is only ∼5 cm (Keller 2005;Ren and Zhu 2013), compared with other sites where the average seeing parameter r 0 is 7 cm (Socas-Navarro et al 2005). To our knowledge, our S-GLAO is the only adaptive optics system that can still provide effective wave-front correction for sunspot high-resolution imaging in such bad seeing conditions, which will significantly improve AO observation efficiency.…”

Science with Large Solar Telescopes: Overview of SpS 6

“…It is interesting to note that many of the new telescopes will enjoy diffraction-limited conditions at near-infrared wavelengths for very large fractions of the observing time (up to 80% for Haleakala! see Socas-Navarro et al (2005))). It is thus expected that much emphasis will be give to (near) IR observations in the coming years.…”