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Measurements made on the components and on two assembled systems of a 2-m Ritchey-Chretien telescope have been used to determine the actual characteristics of the telescope. Sufficient precision has been obtained so that other focal ratio systems can be designed.

In this paper we present the Medium Resolution Spectrograph ESOPO, an instrument designed and built for the 2.1m Telescope at the Observatorio Astronomico Nacional at San Pedro Martir. We discuss the Scientific Goals and the High Level Requirements necessary to translate these goals to optical, mechanical and control specifications. We make an introduction to its conceptual dual-arm design. The optical design is based on a non-classical configuration. The gratings are illuminated in a conical mode working in a quasi Littrow configuration which has the advantage of optimizing the efficiency and the pupil area on the grating. We show here the results of an experimental evaluation of the concept. The optical design, mechanical structure, slit-mask and acquisition system, control systems, and a study of thermal compensators, are discussed briefly, references to more extended contributions in these proceedings are made. The management schematics of the project are briefly discussed.

ESOPO will be a spectrograph of medium resolution for the 2.1 m telescope of the National Observatory at San Pedro Martir, Baja California, Mexico. It has been developed by the Instituto de Astronomia of the Universidad Nacional Autonoma de Mexico (IA-UNAM). The main goal of this instrument is to modernize the capabilities of making science with that particular telescope. It is planned to achieve a spectral resolution between 500 and 5000. ESOPO is split into two arms; each one specialized in a specific wavelength range covering together all the visible light. A very important issue in spectrographs is to avoid inside thermal gradients. Different temperatures in the optical elements produce mechanical movements and image quality degradation during an exposition. The error budget analysis developed for ESOPO allows establishing the required limits for temperature gradients. In this paper is described the thermal analysis of the spectrograph, including specifications, finite element models, thermal equations and expected thermal gradients.

OSIRIS is the optical Day 1 instrument for the 10.4 m GTC telescope. OSIRIS will cover the 365 to 1000 nm spectral range, featuring an 8.6×8.6 arcmin field of view, and capabilities for direct imaging, both long-slit and multiple object spectroscopy, and fast spectrophotometry. The combination of OSIRIS wide field, tunable filters plus charge shuffling array detectors, will constitute the most powerful instrument for studying faint emission-line sources at any redshift. The present contribution gives an overview of the instrument development, currently in its verification phase before commissioning on site. © 2007 Springer.

We investigate the role of industrial replication in the construction of the next generation of spectrographs for large telescopes. In this paradigm, a simple base spectrograph unit is replicated to provide multiplex advantage, while the engineering costs are amortized over many copies. We argue that this is a cost-effective approach when compared to traditional spectrograph design, where each instrument is essentially a one-off prototype with heavy expenditure on engineering effort. As an example of massive replication, we present the design of, and the science drivers for, the Visible IFU Replicable Ultra-cheap Spectrograph (VIRUS). This instrument is made up of 132 individually small and simple spectrographs, each fed by a fiber integral field unit. The total VIRUS-132 instrument covers ~29 sq. arcminutes per observation, providing integral field spectroscopy from 340 to 570 nm, simultaneously, of 32,604 spatial elements, each 1 sq. arcsecond on the sky. VIRUS-132 will be mounted on the 9.2 m Hobby-Eberly Telescope and fed by a new wide-field corrector with a science field in excess of 16.5 arcminutes diameter. VIRUS represents a new approach to spectrograph design, offering the science multiplex advantage of huge sky coverage for an integral field spectrograph, coupled with the engineering multiplex advantage of >102 spectrographs making up a whole.

We present the dual IR camera CID for the 2.12 m telescope of the Observatorio Astronomico Nacional de Mexico, IA-UNAM. The system consists of two separate cameras/spectrographs that operate in different regions of the IR spectrum. In the near IR, CID comprises a direct imaging camera with wide band filters, a CVF, and a low resolution spectrograph employing an InSb 256 x 256 detector. In the mid IR, CID uses a BIB 128 x 128 detector for direct imaging in 10 and 20 microns. Optics and mechanics of CID were developed at IR-Labs (Tucson). The electronics was developed by R. Leach (S. Diego). General design, construction of auxiliary optics (oscillating secondary mirror), necessary modifications and optimization of the electronics, and acquisition software were carried out at OAN/ UNAM. The compact design of the instruments allow them to share a single dewar and the cryogenics system.

OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) is the optical Day One instrument for the 10.4m Spanish telescope GTC to be installed in the Observatorio del Roque de Los Muchachos (La Palma, Spain). This instrument, operational in mid-2004, covers from 360 up to 1000 nm. OSIRIS observing modes include direct imaging with tunable and conventional filters, long slit and multiple object spectroscopy and fast spectrophotometry. The OSIRIS wide field of view, high efficiency and the new observing modes (tunable imaging and fast spectrophotometry) for 8-10m class telescopes will provide GTC with a powerful tool for their scientific exploitation. The present paper provides an updated overview of the instrument development, of some of the scientific projects that will be tackled with OSIRIS and of the general requirements driving the optical and mechanical design.

We present the optical design of the f/1 camera for the Hobby-Eberly Telescope Low Resolution Spectrograph Infrared Extension (LRS-J). This instrument extends the coverage of the LRS to 1300 nm by adding a fast cryogenic camera and volume holographic grisms (VPHG) to the LRS. This approach enables new science without the expense of building a complete new instrument. The camera is a catadioptric Maksutov type design, based on that of the optical LRS, that uses a HAWAII-1 1024x1024 detector. The design succeeds in imaging virtually all the light into one pixel over the HET field of view (FOV) and the wavelength range 900-1300 nm. We discuss the challenges of designing and manufacturing a fast camera for cryogenic use, and give details of the tolerance analysis.

During the GTC integration phase, the Commissioning Instrument (CI) will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature WFS, and high resolution Shack-Hartmann WFS. After the GTC Commissioning we also plan to install a Pyramid WFS. This instrument can therefore serve as a test bench for comparing co-phasing methods for ELTs on a real segmented telescope. In this paper we made a general instrument overview.

The Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) has been designed as a Day-One optical instrument for the 10.4-m Gran Telescopio Canarias (GTC). Its conceptualization started as early as 1998. This contribution summarizes how the evolution of the OSIRIS concept forced the optical design to successfully respond to ever-harder challenges. It will be the first instrument, on such a large telescope, belonging to a new class of tunable imager, using tunable filters (TFs), and a single slit and multi-object low-resolution spectrograph. These features combined with charge shuffling capabilities, covering the optical wavelength range (365-1000 nm). OSIRIS, to be first mounted at one of GTC's Nasmyth platforms, is designed to be compact enough to fit at the Cassegrain focus as well. The optical design is devised around the classical concept of collimator plus camera. The collimator is an off axis ellipsoidal mirror, while the f/2.475 camera consists of several groups of all spherical surfaces lenses, forming a unit together with the detector and cryocooler. A folder mirror prevents interference with the GTC acquisition and guiding subsystem. Several combinations of color and interference filters, TFs and grisms are available in the collimated beam, near the pupil, to provide the wide versatility of required observing modes and resolutions. Short descriptions of the OSIRIS geometry, specifications and the optical design are presented, with emphasis in the strategy followed in the design process.