#Hexaflex flexture full

The corrector is at the heart of a new powerful 400-fiber spectroscopic survey facility known as the 2dF.

#Hexaflex flexture full

It is a 4-element design, the first two elements being rotatable cemented prismatic doublets approaching 1.0 m in diameter, which permit full atmospheric dispersion compensation to high zenith distances. The corrector is capable of producing aberration-corrected images over a full 2 degree diameter field of view. The Anglo-Australian Telescope has just received a new prime- focus corrector, designed by Damien Jones (Prime Optics, Qld., Australia) and manufactured by Contraves, USA. Comparisons may be made both across spectrometer types and as a design guide within a family, where options must be evaluated. At a minimum, it incorporates the oft neglected instrument response and transmission/efficiency parameters (such as with a grating). This new figure of merit maximizes the potential information content at the spectrograph focal plane. In both the first and higher order optics sense, A(Omega) R is investigated and compared with a better figure of merit. It is shown that A(Omega) R is no longer a constant as the entrance `slit' is varied. A traditional figure of merit for spectrographs is the throughput-resolution product (A(Omega) R). However, the nature of these spectrographs pose new questions of certain design parameters.

They offer the principle advantages of increasing the number of objects with which simultaneous spectra may be recorded, better stability, an improvement in versatility, and factors associated with the mode-scrambling properties of fibers. We describe focal ratio degradation tests of a variety of optical fibers and the design of the `pseudoslit' which mounts the fibers in a line at the input to the conversion optics.įiber-fed spectrographs have now been employed in astronomy for several years.

The conversion optics are mounted at the entrance to the spectrograph. A simple optical system has been designed that converts the light from the fibers into the f/ratio expected by the spectrograph. If the 4/8 spectrograph were fed directly with this f/4.5 beam approximately 68% of the light would be lost. Fibers from a robotic fiber-positioner at prime focus degrade the f/5.5 beam from the telescope (after it has passed through a wide-field prime focus corrector) into roughly a f/4.5 beam. The spectrography forms part of the automated Multi- Object Spectrograph system developed as a collaboration between UCO/Lick Observatory and the Lawrence Livermore National Laboratory. We describe the conversion of an existing f/8 Cassegrain spectrograph to a floor-mounted spectrograph fed by 94 fibers from the f/5 prime focus of the Shane 3-meter telescope at Lick Observatory. At best, the RMA can reach one third of the number of fibers. The impacts on the performances, described in terms of `Realizable Multiplex Advantage' (RMA) is described. General observing modes are briefly reviewed. The observation wavelength must be properly related to the acquisition and guiding wavelengths, constraining the use of filters (5) Other observational constraints like sky subtraction or high spectral stability can lead to specific observational procedures. Chromatic dispersion is shown impossible to calibrate out. With these characteristics, some observational aspects are investigated: (1) The (blind) positioning error budget constrains the astrometry to within 0.2' rms to keep photon losses at an acceptable level (2) All-sky atlases from Schmidt plate scans, when available, will provide the relevant information for most programs (3) Cross- identification or special observing procedures may be required for guide stars if they have a different origin than targets (4) Atmospheric effects are investigated. Crude anticipation of future programs on these instruments allows to predict that targets will be mainly point sources or of low extension, with magnitudes up to approximately 22. The scientific objectives of multi-object fiber instruments on 8 m class telescopes may significantly depart from those carried out on 4 m class telescopes.