Wide-field resolution uniformity for solar ground-layer adaptive optics

Ground-layer adaptive optics (GLAO) has significant potential for solar observations of ground-based telescopes due to its ability to provide wide field-of-view (FOV) correction. Ground-based telescopes always pursue high spatial resolution to improve observational quality, which is typically evaluated by the full width at half maximum of the point spread function. However, GLAO system also requires uniform spatial compensation across a wide FOV, particularly for accurate solar magnetic field topology and speckle imaging techniques. Multiple guide stars (GS) are used to detect ground-layer turbulence, and their layout greatly influences observational quality. To this end, in this paper, we optimize the GS layout to improve spatial resolution uniformity for wide-field GLAO. Specifically, we propose a novel wide-field resolution uniformity metric to evaluate the observational quality in GLAO system. Based on this innovative metric, simulations identify two effective GS configurations: the center + ring GS layout achieves higher resolution, and the single ring GS layout exhibits more uniform correction across a wide FOV (improving 41.4% resolution uniformity by trading 2.2% average resolution). To validate this result, we conduct the indoor experiment and on-sky observation. An indoor solar GLAO platform is designed and constructed. Experiments show good agreement with our simulation results. Our on-sky observation is conducted on the 1-m New Vacuum Solar Telescope. GSs in a ring layout improve uniformity by 18.70%, although this comes with a 16.25% reduction in the generalized Fried parameter compared with the center + ring GS layout.