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.