Paul L. Byard

The Multi-Object Double Spectrographs for the Large Binocular Telescope

The Multi-Object Double Spectrographs (MODS) are two identical high-throughput optical low- to medium-resolution CCD spectrometers being deployed at the Large Binocular Telescope (LBT). Operating in the 340-1000nm range, they use a large dichroic to split light into separately-optimized red and blue channels that feature reflective collimators and decentered Maksutov-Schmidt cameras with monolithic 8×3K CCD detectors. A parallel infrared laser closed-loop image motion compensation system nulls spectrograph flexure giving it high calibration stability. The two MODS instruments may be operated together with digital data combination as a single instrument giving the LBT an effective aperture of 11.8-meter, or separately configured to flexibly use the twin 8.4-meter apertures. This paper describes the properties and performance of the completed MODS1 instrument. MODS1 was delivered to LBT in May 2010 and is being prepared for first-light in September 2010.

Ohio State Infrared Imager/Spectrometer (OSIRIS)

The Ohio State Infrared Imager/Spectrometer (OSIRIS) is a general purpose near infrared (0.9 to 2.5 micrometers ) instrument that can be used at a wide variety of telescope focal planes. OSIRIS currently uses a 256 X 256 HgCdTe array detector and will accommodate larger arrays when available. OSIRIS has two modes of operation: imaging and spectroscopic. This paper describes the general instrument design and sample scientific results.

A Novel Double Imaging Camera (ANDICAM)

We describe an instrument that is capable of taking simultaneous images at one optical (UBVRI) and one near-infrared (JHK) wavelength. The instrument uses relatively simple optics and a dichroic to image the same field on to an optical CCD and an HgCdTe array. The mechanical and thermal design is similar to previous instruments built by our group and the array controllers are based on the same architecture. The instrument has been in use for the past four years on the CTIO/Yale 1m telescope in Chile and has an excellent operational/reliability record. A number of notable science results have been obtained with the instrument; especially interesting are several photometric monitoring projects that have been possible, since the instrument is available every night on the telescope.

MDM/Ohio State/ALADDIN infrared camera (MOSAIC)

The MDM/Ohio State/ALADDIN IR Camera (MOSAIC) is a general purpose near IR imaging camera and medium-resolution long- slit spectrometer in use on the MDM 1.3-m and 2.4-m telescopes and the Kitt Peak 2.1-m and 4-m telescopes. In cooperation with NOAO and USNO, MOSAIC is one of the first general-purpose near-IR instruments available to the astronomical community that uses a first-generation 1024 X 512 ALADDIN InSb array, with the capability to use a full 1024 X 1024 array once one becomes available. MOSAIC provides tow imaging plate scales, and a variety of long- slit grism spectroscopic modes. This paper describes the general instrument design and capabilities, and presents representative scientific results.

MODS : Optical design for a Multi-Object Dual Spectrograph

The paper describes the optical design for the Multi Object Dual Spectrograph (MODS) for the Large Binocular Telescope (LBT). MODS is designed to cover the entire spectrum accessible to silicon CCDs from a ground-based telescope with the highest possible throughput. Multi-object capability is available using 0.6 arc-minute in diameter with reduce image quality. Under the very best seeing conditions and with the LBT adaptive optics in operation, slit widths of 0.3 arc-seconds can be used to enhance the resolving power and/or reduce the background. The optical path is divided into blue and red channels by a dichroic beam splitter following the slit masks. The blue channel covers a wavelength range from the atmospheric cut-off at approximately 300 nm to approximately 550 nm while the red channel covers the range from approximately 550 nm to the limit of useful sensitivity of silicon CCDs. This approach allows the optimization of transmissive and reflective coatings to provide the very highest throughput for each channel. The design is conventional in the use of reflective parabolic collimators. However, the cameras are designed as decentered Schmidt/Maksutovs with large aspheric coefficients for the inner surfaces of the correctors. This approach enables the field flatteners and detector to be positioned outside the beam entering the camera where it will not vignette. Figures are presented showing image quality for imaging and spectrographic modes.

RETROCAM: A Versatile Optical Imager for Synoptic Studies

We present RETROCAM, an auxiliary CCD camera that can be rapidly inserted into the optical beam of the MDM 2.4 m telescope. The speed and ease of reconfiguring the telescope to use the imager and a straightforward user interface permit the camera to be used during the course of other observing programs. This in turn encourages RETROCAMs use for a variety of monitoring projects.

The variability of the spectrum of Arakelian 120

New spectroscopic and photometric observations of the variable Seyfert 1 galaxy Arakelian 120 are presented. These data are supplemented with published data from other sources. It is shown that Akn 120 exhibits both short-term and long-term variability, as do other Seyfert galaxies. The flux in the broad H..beta.. emission line closely follows the optical continuum flux, which provides strong support for photoionization models and implies that the broad-line emitting region is very small (less than approx.0.04 pc in extent).

A multi-object double spectrograph for the Large Binocular Telescope

We are building a Multi-Object Double Spectrograph for the Large Binocular Telescope. The instrument is designed to have high throughput from 320 to 1000 nm, spectral resolutions of 1,000-10,000, and multi-object capability over a 6 arcminute field. The design incorporates a dichroic and splits the science beam into a blue and a red channel, each of which can illuminate an 8,192 pixel long detector (with 15 micron pixels) with good image quality. The highly modular design can hold up to three gratings and an imaging flat and a selection of filters in each channel, all of which are quickly accessible; this allows for substantial observing flexibility. Progress on the construction of the instrument and future plans will be described.

On-sky performance of the Multi-Object Double Spectrograph for the Large Binocular Telescope

The Multi-Object Double Spectrographs (MODS) are two identical high-throughput optical dichroic-split double-beam low- to medium-dispersion CCD spectrometers being deployed at the Large Binocular Telescope (LBT). They operate in the 3200-10500Å range at a nominal resolution of λ/δλ≈2000. MODS1 saw first-light at the LBT in September 2010, finished primary commissioning in May 2011, and began regular partner science operations in September 2011. MODS2 is being readied for delivery and installation at the end of 2012. This paper describes the on-sky performance of MODS1 and presents highlights from the first year of science operations.

The Ohio State Imaging Fabry-Perot Spectrometer (IFPS)

The Ohio State University Imaging Fabry-Perot Spectrometer (IFPS) is designed for two-dimensional imaging spectrophotometric and kinematic studies in the wavelength range of 3400-10000A. Presently it uses four etalons providing low and medium spectral resolutions (lambda/delta-lambda) of 1200 in the 4500-7500A wavelength range, and lambda/delta-lambda=4500 in three bands covering the 3400-4000A, 4100-5500A, and 6000-7000A wavelength regions. These resolutions make it applicable to a wide range of galactic and extragalactic imaging spectrophotometry problems. The IFPS has also found use as direct imaging focal camera (without the etalons). The instrument development and basic design philosophies are described, and some scientific results from the Fabry-Perot mode of the instrument are presented.