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I am trying to find the wavelength solution for a set of echelle data using dohydra. Ideally, I would like to fit lines to all but the bluest 20 angstroms of my spectral range. Is there any way of setting a limited range in the dohydra step without actually trimming the image?Thank you.

Frank is the best person to reply, but one way to "trim" an image without physically making another copy is to pass in an image section containing the data you want. This effectively removes the pixels on input and the output image should be the trimmed size.-Mike