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Publications (14)10.35 Total impact

  • Tim Hardy, Marc R. Baril, James Stilburn
    03/2006;
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    ABSTRACT: A wide-field low-resolution multi-object optical spectrograph suitable for a 30-m F/15 telescope is described. The effort to build a 30-m class telescope is gaining momentum. Many science cases for such a telescope make the need for a wide-field seeing-limited spectrograph a high priority. Our concept comprises four identical instruments placed symmetrically around the optical axis of the telescope, this allows smaller dimensions for the spectrographs and their components. Each instrument is placed in one quadrant of the telescope focal plane; a space at the center of the field is free for other instrumentation. Using a dichroic beam-splitter each instrument feeds a "red" and "blue" camera. The total field is 81 square arcmin, the wavelength range covers simultaneously 310 nm to 1000 nm and the spectral resolution (R) is 300 to 5000. The instruments are designed for vertical mounting at a Nasmyth focus to avoid gravity vector changes and reducing mechanical flexure problems during observation. The layout also allows access to internal components for maintenance. The design offers advantages for the location of a slit mask and filters. The instruments can also be used for imaging. Optical and opto-mechanical models and analyses are presented with specifications and expected performance.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    09/2004;
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    ABSTRACT: A wide-field low-resolution multi-object optical spectrograph suitable for a 30-m F/15 telescope is described. The effort to build a 30-m class telescope is gaining momentum. Many science cases for such a telescope make the need for a wide-field seeing-limited spectrograph a high priority. Our concept comprises four identical instruments placed symmetrically around the optical axis of the telescope, this allows smaller dimensions for the spectrographs and their components. Each instrument is placed in one quadrant of the telescope focal plane; a space at the center of the field is free for other instrumentation. Using a dichroic beam-splitter each instrument feeds a "red" and "blue" camera. The total field is 81 square arcmin, the wavelength range covers simultaneously 310 nm to 1000 nm and the spectral resolution (R) is 300 to 5000. The instruments are designed for vertical mounting at a Nasmyth focus to avoid gravity vector changes and reducing mechanical flexure problems during observation. The layout also allows access to internal components for maintenance. The design offers advantages for the location of a slit mask and filters. The instruments can also be used for imaging. Optical and opto-mechanical models and analyses are presented with specifications and expected performance.
    Proc SPIE 09/2004;
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    ABSTRACT: The first of two Gemini Multi Object Spectrographs (GMOS) has recently begun operation at the Gemini-North 8m telescope. In this presentation we give an overview of the instrument and describe the overall performance of GMOS-North both in the laboratory during integration, and at the telescope during commissioning. We describe the development process which led to meeting the demanding reliability and performance requirements on flexure, throughput and image quality. We then show examples of GMOS data and performance on the telescope in its imaging, long-slit and MOS modes. We also briefly highlight novel features in GMOS that are described in more detail in separate presentations, particularly the flexure compensation system and the on-instrument wavefront sensor. Finally we give an update of the current status of GMOS on Gemini-North and future plans.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    03/2003;
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    ABSTRACT: The Gemini Multi-Object Spectrograph (GMOS) was delivered and commissioned at the Gemini North Observatory and it has been in regular science use since November 2001. While GMOS-North met all its reliability and performance requirements on flexure, image quality and throughput, the high velocity precision (2 km/sec) mode will not be implemented until the Atmospheric Dispersion Compensator/Corrector (ADC) is delivered and commissioned. The ADC optical design incorporating two bonded prism pairs and two corrector lenses is described along with its opto-mechanical and software control design considerations as related to the overall system requirements including: image quality, error budget, optical mounting, opto-mechanical packaging, mechanism control, handling, deployment and telescope observational control considerations.
    Proc SPIE 03/2003;
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    ABSTRACT: The Gemini Multiobject Spectrographs (GMOS) were designed to take advantage of the exquisite image quality expected of the Gemini telescopes. To achieve this, two of the many requirements placed on the optical system was that it not degrade the best image quality expected of the telescope by more than 10% while delivering a throughput of about 80% over the entire 0.4-1 mum waveband. In this paper, key components of the design and execution of this optical system are discussed and test results are presented demonstrating that it meets these requirements on Gemini today. Among other characteristics, we look at the image quality performance as a function of colour and field angle, the measured throughput, and the focalplane flatness on the detectors.
    Proc SPIE 01/2003;
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    ABSTRACT: Extensive results from the commissioning phase of PUEO, the adaptive optics instrument adaptor for the Canada--France--Hawaii telescope (CFHT), are presented and discussed. Analyses of more than 750 images recorded with a CCD and a near-IR camera on 16 nights in wavelengths from B to H are used to derive the properties of the compensated wavefront and images in a variety of conditions. The performance characteristics of the system are analyzed and presented in several ways, in terms of delivered Strehl ratios, full-width-half-maxima (FWHM), and quantities describing the improvements of both. A qualitative description is given of how the properties of the corrected images result from the structure function of the compensated phase. Under median seeing conditions, PUEO delivers essentially diffraction--limited images at H and K, images with FWHM¸0: 00 1 at J and I , and provides significant gains down to B, with guide stars as faint as R = 14. During good conditions, substantial gain...
    Publications of the Astronomical Society of the Pacific 04/1999; · 3.69 Impact Factor
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    ABSTRACT: Extensive results from the commissioning phase of PUEO, the adaptive optics instrument adaptor for the Canada-France-Hawaii telescope, are presented and discussed. Analyses of more than 750 images recorded with a CCD and a near-IR camera on 16 nights in wavelengths from B to H are used to derive the properties of the compensated wavefront and images in a variety of conditions. The performance characteristics of the system are analyzed and presented in several ways, in terms of delivered Strehl ratios, full-width-half-maxima, and quantities describing the improvements of both. A qualitative description is given of how the properties of the corrected images result from the structure function of the compensated phase. Under median seeing conditions, PUEO delivers essentially diffraction-limited images at H and K, images with FWHM ~0.1" at J and I, and provides significant gains down to B, with guide stars as faint as R = 14. During good conditions, substantial gains were realized with guide stars as faint as R = 17. A simple user-interface and software which automatically and continuously optimizes the mode gains during observations makes the operational efficiency extremely high. A few astronomical examples are briefly discussed.
    01/1998;
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    ABSTRACT: The multiobject spectrograph is the only instrument to be duplicated and available at both GEMINI North and South.
    Experimental Astronomy 11/1997; 7(4):293-299. · 2.97 Impact Factor
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    ABSTRACT: A description is given of the design and performance of a quadrant detector offering improvements in sensitivity and ease of construction over earlier devices. The optics are compact, and low-noise high-sensitivity operation is achieved with the use of avalanche photodiode detectors. The device is installed on the SIS spectrograph on the CFH 3.6-m telescope and allows image stabilization to be achieved by a tip-tilt mirror system using guide stars as faint as magnitude 18.5.
    Publications of the Astronomical Society of the Pacific 09/1997; 109:1165-1166. · 3.69 Impact Factor
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    ABSTRACT: The two Gemini multiple object spectrographs (GMOS) are being designed and built for use with the Gemini telescopes on Mauna Kea and Cerro Pachon starting in 1999 and 2000 respectively. They have four operating modes: imaging, long slit spectroscopy, aperture plate multiple object spectroscopy and area (or integral field) spectroscopy. The spectrograph uses refracting optics for both the collimator and camera and uses grating dispersion. The image quality delivered to the spectrograph is anticipated to be excellent and the design is driven by the need to retain this acuity over a large wavelength range and the full 5.5 arcminute field of view. The spectrograph optics are required to perform from 0.36 to 1.8 microns although it is likely that the northern and southern versions of GMOS will use coatings optimized for the red and blue respectively. A stringent flexure specification is imposed by the scientific requirement to measure velocities to high precision (1 - 2 km/s). Here we present an overview of the design concentrating on the optical and mechanical aspects.
    Proc SPIE 03/1997;
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    ABSTRACT: The fabrication requirements of the Gemini multi-object spectrograph (GMOS) slit mask is discussed particularly in terms of the slit-to-slit position, slit geometry and the telescope operation. The demand for precision slit masks with high quality slits of width of less than quarter arcsecond and an allowable fabrication time of two hours required examination of innovative fabrication processes and mask materials. Different fabrication processes including high precision cutting processes, water-jet and laser machining systems are evaluated according to cost, speed and efficiency, and the findings are documented. Different candidate mask materials including low thermal expansion metals and novel materials such as graphite paper and carbon-fiber composite sheet, are evaluated according to their relevant mechanical and physical properties, and the findings are also documented. In addition to identifying that the most suitable mask material is unidirectional carbon fiber sheet and the corresponding fabrication process is a Nd:YAG laser machining system, the mask handling system for GMOS is described and methodology to minimize systematic fabrication errors is also proposed.
    Proc SPIE 03/1997;
  • Adaptive Optics; 01/1996
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    ABSTRACT: Infrared (IR) observations have traditionally been limited to a relatively small number of specialized telescopes since: (1) the cost of detectors and detector system development is large; and (2) there are a number of significant technical differences associated with an 'infrared-capable' telescope when compared to a traditional optical telescope. With the advent of lower cost infrared detectors in recent years, IR instrumentation now becomes accessible to observatories with budgets unable to support the traditional high costs. We have assembled a complete observing system making use of a Hughes 256 X 256 pixel PtSi 1 - 5 micron array detector. This particular PtSi detector was chosen because it has several characteristics conducive to precise photometric observations. The detector has 100% fill factor, a large dynamic range of 10(superscript 4), low dark current and the potential for extremely good stability. The system we describe was designed with an emphasis on simplicity and the use of commercially available hardware and software, while retaining full performance of the detector. The system proved to integrate easily into the CCD observing environment used on our telescopes.
    Proc SPIE 01/1993;