ESO Exposure Time Calculators

ESO organizes exposure calculations by telescope, instrument and imaging/spectroscopy mode, marking older ETC1 routes as deprecated or migrated. ETC 2.0 documents copying the input form as JSON, changing parameters and obtaining JSON output through its API; a separate converter produces ASCII. The API validates inputs, but ESO says the web form provides more comprehensive interactive constraints, so use that instrument's form to check supported ranges and combinations. A detector-saturation warning covers the instrument mode's whole wavelength region even when a plot shows only part of it. Retain the instrument configuration and full wavelength scope with an exposure comparison; the index also links formula and efficiency references.