.mt file convert to .fits/.ascii/.dat How to convert .mt file with a spectrum to a more convenient format, please? I am able to display that in fv: Fits Viewer, but I am lost in converting. Thank you
.mt files are the output files (or possibly intermediate ones as the final products in the ESO archive have .fits extensions) produced by the ESO-MIDAS data reduction system for the (in this case) FEROS echelle spectrograph. The individual echelle orders have been extracted from the original 2D CCD images, flattened, wavelength calibrated and joined together into a 1D spectrum.
The .mt files are FITS files however the fact that they are 1D can cause some issues for normal image viewers; the ESO archive has some help on how to setup various tools (including fv) for displaying 1D spectra. In this case, since the file is a standard FITS file, regular FITS tools e.g. AstroPy, IRAF, MIDAS etc will work to convert the file and the ESO archive link above has info on how to do this in Python, IDL and IRAF.
One relatively pain-free option could to use Splat-VO to do the plotting, investigation and conversion. (When loading the .mt spectrum you will need to either rename the extension to .fits or tell Splat-VO the file format is FITS as it won't be auto-recognized). Once it's loaded in, you can convert to a variey of formats, including ASCII/text.