中国科学院云南天文台机构知识库

抚仙湖1 m新真空太阳望远镜(New Vacuum Solar Telescope,NVST)利用多波段成像系统对太阳光球和色球同时进行高分辨成像观测,并对观测图像进行多波段同步高分辨统计重建,以大幅度降低重建所需的计算量,并改善低信噪比波段的高分辨重建效果。大气色散是影响多波段同步高分辨重建效果的主要因素。借助多层湍流大气的模拟,通过比较不同天顶角下色散引起的波像差、相对谱比,分析了大气色散对多波段同步高分辨重建的影响。分析结果表明对于1 m太阳望远镜,当天顶角在60°以内时,色散对近红外以及波长相差不大的可见光波段的多波段同步高分辨重建的影响较小,而393.3 nm波段受色散的影响明显,天顶角超过45°时分辨率明显下降。

The New Vacuum Solar Telescope (NVST) at the Fuxian Solar Observatory (of the Yunnan Observatories) is currently equipped with a two-channel imaging system, which enables the NVST to simultaneously collect solar images at the wavelengths of the Tio and H-αlines.Plans have been made to extend the number of channels of the imaging system to five.The extension will inevitably increase the amount of calculations required for image reconstruction.This, coupled with the calculation-intensive speckle-masking method used for the NVST, can potentially result in calculations beyond what the current systems can handle within reasonably short times.In this paper, we present a new image-reconstruction method, termed as the Solar Multi-Waveband Synchronous High-Resolution Reconstruction (SMWSHRR).The SMWSHRR first estimates the PSF of a channel at which data have relatively high signal-to-noise ratios (SNRs), then by applying wavelength corrections to the PSF obtains the PSF of each other channel.With the evaluated PSFs it finally deconvolves images of all channels simultaneously to save time.Using the data of high SNRs as the basis gives the method an advantage of improving the reconstruction accuracy.However, the method assumes that light rays of all relevant wavelengths follow the same atmospheric path.Practical patterns of light-ray paths deviate from the assumption, and effects of deviations on reconstruction results need to be studied.In this paper, through simulations of turbulences in multiple layers of the atmosphere we analyze influences of atmospheric dispersion on results of the SMWSHRR.The analyses are based on comparisons of the wavefront aberrations caused by atmospheric dispersion, the relative spectral ratios, and the reconstructed images at different zenith-angle values.Our results show that for a 1m solar telescope as the NVST, atmospheric dispersion at most weakly affects results of the SMWSHRR in near-infrared and visual wavebands as long as the zenith angles are less than 60°, except that result resolutions at 393.3nm will be appreciably reduced if zenith angles are above 45°.