  We present the design and testing of a prototype in-plane echelle
spectrograph based on an actively controlled fibre-fed double-pass design. This
system aims to be small and efficient with the minimum number of optical
surfaces - currently a collimator/camera lens, cross-dispersing prism, grating
and a reflector to send light to the detector. It is built from catalogue
optical components and has dimensions of approximately 20x30 cm. It works in
the optical regime with a resolution of >70,000. The spectrograph is fed by a
bifurcated fibre with one fibre to a telescope and the other used to provide
simultaneous Thorium Argon light illumination for wavelength calibration. The
positions of the arc lines on the detector are processed in real time and
commercial auto-guiding software is used to treat the positions of the arc
lines as guide stars. The guiding software sends any required adjustments to
mechanical piezo-electric actuators which move the mirror sending light to the
camera removing any drift in the position of the arc lines. The current
configuration using an sCMOS detector provides a precision of 3.5 milli-pixels
equivalent to 4 m/s in a standard laboratory environment.
