A coarse-to-fine strategy for the registration of the multi-wavelength high-resolution solar images

Abstract

Abstract The registration of multi-wavelength high-resolution solar images is an important task in the research of solar physics. This paper proposed a coarse-to-fine strategy to realize the accurate registration of high-resolution photospheric images and chromospheric images observed by the New Vacuum Solar Telescope (NVST) whose field-of-view is about 2′ ∼ 3′, and the spatial resolution can reach 0.1″ after image reconstruction. In this strategy, the full-disk solar images with relatively lower resolution taken by other space- or ground-based telescopes are taken as transition images, and the Fourier-Merlin transform, Template matching and a local statistical information based algorithm are used in combination. After registration, the geometric transformation between multi-wavelength images of NVST are corrected at the level of sub-arcseconds, including the rotation, scaling and translation relations. Two sets of data observed in active regions (i.e., the NOAA 11982 and the NOAA 12673) are used to illustrate our method step by step. The result shows that the registration accuracy can reach less than 1″. Moreover, this work also has facilitated the combination of high-resolution observations of NVST with the continuum, ultraviolet passbands and magnetic field observations of the Solar Dynamic Observation (SDO), which is highly beneficial to the multi-instrument joint measurement of solar activities.