This upgrade kit for the eShel spectrograph replaces the instrument’s collimator with a new doublet. This new optical component is optimized to increase the range of the spectral domain achievable, in particular in the blue part of the spectrum.
With this upgrade, the eShel spectroscope allows observations from 4000A! The replacement of the collimator module is quite simple: only three screws to remove. This upgrade kit is only useful for eShel delivered before June 2018. All eShel delivered since this date include the new collimator.