Stray-Light and Space PSF Measuring of the Multi-Band Spectrometer of the 1m New Vacuum Solar Telescope

Stray-light is caused by the scattering of optical surfaces and the Earth's atmosphere; which degrades the spatial resolution of spectral images. Almost every optical system is affected by stray-light. To obtain high-resolution spectral images, we need to eliminate the effect caused by stray-light as much as possible. The stray-light of multi-waveband spectrometer can be divided into two categories:(1) stray-light caused by the scattering of the optical and mechanical structures in the spectral barrel and (2) stray-light mixed in the imaging optical path and participating in dispersion. The first category can be measured directly, and it accounts for 3% of spectral energy. It is difficult to measure the second category precisely because it could be affected by many factors. We measured the stray-light around the target from the eclipse spectral observation, and found that the lower limit of the stray-light was about 10%. In addition, we measured the point spread function (PSF) of the multi-band spectrometer in the space direction. This work would provide reference for future high-resolution spectrum reconstruction.