Instrument Characteristics
In this section we review the essential components and characteristics of the LUCI instruments. The LUCI instruments share a common optical design, differing only slightly in their “as built” configurations. The LUCI’s are located at the f/15 Front Bent Gregorian Focal Stations, LUCI1 on the left (SX) station and LUCI2 on the right (DX). The instruments are kept on the telescope under vacuum and cooled by two closed-cycle He coolers that are synchronized in such a way as to minimize vibrations transmitted to the telescope.
The following pages will review the optical components of the LUCI instruments.
Optical Path
Light is passed to the Front Bent Gregorian focal station, through the LUCI dichroic dewar entrance. The entrance windows each have a slightly different cut: 0.89 microns (LUCI1) and 0.95 microns (LUCI2).
Longslit and user created multi-slit masks are stored in a cabinet in LUCI and can be placed in the Focal Plane. The MOS Unit is contained within the instrument, kept under vacuum and cryogenically cooled.
The four fold mirrors overall keep the instrument compact. The last of the 4 fold mirrors (FM4) is used to close either a passive (from a lookup table) or active (from fiducial marks on the masks) flexure compensation loop to correct internal flexure within the instruments that occurs with changes in elevation or rotation.
Three gratings are available, working in different resolution regimes spanning from low (R ∼ a few hundred) to medium (R < 30000) resolution. Three interchangeable cameras (N1.8, N3.75, N30) in each instrument produce different pixel scales on the Hawaii 2RG detectors. These are primarily for spectroscopy, imaging, and adaptive optics, respectively.
Variations of the optical setup allow for the LUCI instruments to do seeing-limited imaging, multi-object and longslit spectroscopy over a 4′ by 4′ field of view, as well as diffraction-limited imaging and longslit spectroscopy over a 30″ by 30″ field of view.
