Molecfit: A Package for Telluric Absorption Correction
  Correcting for the sky signature usually requires supplementary calibration data which are very expensive in terms of telescope time. In addition, the scheduling flexibility is restricted as these data have to be taken usually directly before/after the science observations due to the high variability of the telluric absorption which depends on the state and the chemical composition of the atmosphere at the time of observations. Therefore, a tool for sky correction, which does not require this supplementary calibration data, saves a significant amount of valuable telescope time and increases its efficiency. We developed a software package aimed at performing telluric feature corrections on the basis of synthetic absorption spectra. 
W. Kausch, S. Noll, A. Smette, S. Kimeswenger, H. Horst, H. Sana, A.   Jones, M. Barden, C. Szyszka, and J. Vinther
astro-ph.IM