Convolution and Deconvolution

Estimating the instrumental point spread function and correcting the observed spectra for the instrumental profile by deconvolution  is a delicate subject. Here, the available tools are only briefly mentioned. The point spread function (PSF) can be estimated from the observations ( e.g., from the profile of suitable lines in the comparison, night sky, or interstellar medium spectrum), possibly using the fitting package if a noise-free, analytical approximation is desired. Once this is done, the command DECONVOLVE/IMAGE can be applied to deconvolve the observed data. Conversely, the convolution  of, e.g., a synthetic spectrum with the PSF can be done with the command CONVOLVE.