Latest Results and Developments with the Hercules Spectrograph at Mt John Observatory

摘要

The Hercules spectrograph is a fibre-fed vacuum echelle spectrograph at Mt John Observatory in New Zealand, designed for high precision measurements of stellar radial velocity. It first came into operation in 2001. Since then we have routinely achieved long-term radial-velocity stability of about 15 m/s on sharp-lined late-type stars. Over the last few years we have (i) added a new 4k x 4k CCD giving full wavelength coverage from 360 to 900 nm in one exposure; (ii) supplied a new video camera for acquisition and guiding; (iii) thermally stabilized the Hercules room to about ±0.1 deg C; (iv) built a remotely controlled CCD focusing device with digital readout to±10 microns;(v) designed a fibre double scrambler;(vi) done tests with an iodine cell, showing that radial-velocity precision of 2.5 m/s can readily be achieved. This is close to the photon-noise limit.