A correction method for the telluric absorptions and application to Lijiang Observatory

Observing a telluric standard star for correcting the absorption lines of spectrum will take significant amount precious telescope time, especially in long-term spectral monitoring project. Beyond that, it's difficult to select suitable near both time and airmass scientific object. In this paper, we present method by combining advantages long slit spectroscopy. By rotating slit, observed object nearby comparison one exposure, so that spectra objects should have same transmission spectrum. The was constructed dividing its stellar template, used correct Using spectrograph Lijiang 2.4-meter telescope, designed spectroscopic observation strategy, finished four-year pair (an active galactic nuclei an non-varying star). We applied monitored investigated variation absorptions at Observatory. found transparency is mainly modulated seasonal variability relative humidity, seeing. scatter [O~III] $\lambda$5007 fluxes emitted from narrow-line region as indicator, correction accuracy 1%.