Austin, TX, United States
Austin, TX, United States
SEARCH FILTERS
Time filter
Source Type

Green R.F.,Binocular
Proceedings of the International Astronomical Union | Year: 2012

IAU Resolution 2009 B5 calls on IAU members to protect the public's right to an unpolluted night sky as well as the astronomical quality of the sky around major research observatories. The multi-pronged approach of Commission 50 includes working with the lighting industry for appropriate products from the solid state revolution, arming astronomers with training and materials for presentation, selective endorsement of key protection issues, cooperation with several other IAU commissions for education and outreach, and provision of clear quantitative priorities for outdoor lighting standards. © 2015 International Astronomical Union.


Schmid T.,University of Central Florida | Rolland J.P.,University of Central Florida | Rolland J.P.,University of Rochester | Rakich A.,Binocular | Thompson K.P.,Optical Research Associates
Optics Express | Year: 2010

We present the nodal aberration field response of Ritchey-Chrétien telescopes to a combination of optical component misalignments and astigmatic figure error on the primary mirror. It is shown that both astigmatic figure error and secondary mirror misalignments lead to binodal astigmatism, but that each type has unique, characteristic locations for the astigmatic nodes. Specifically, the characteristic node locations in the presence of astigmatic figure error (at the pupil) in an otherwise aligned telescope exhibit symmetry with respect to the field center, i.e. the midpoint between the astigmatic nodes remains at the field center. For the case of secondary mirror misalignments, one of the astigmatic nodes remains nearly at the field center (in a coma compensated state) as presented in Optics Express 18, 5282-5288 (2010), while the second astigmatic node moves away from the field center. This distinction leads directly to alignment methods that preserve the dynamic range of the active wavefront compensation component. © 2010 Optical Society of America.


Rakich A.,Binocular
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The Optical Plate Diagram of C. R. Burch has been generalized to allow the calculation of third-order perturbation aberrations for nominally axially symmetrical optical systems. The plate method has the advantage of simplifying the third-order analysis of optical systems by removing the first-order considerations that complicate traditional approaches. This development is shown to be directly analogous to the original derivation of Shack and Thompson. © 2010 Copyright SPIE - The International Society for Optical Engineering.


Rakich A.,Binocular | Thompson D.,Binocular | Kuhn O.P.,Binocular
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

The Large Binocular Telescope (LBT) consists of two 8.4 m telescopes mounted on a common alt-az gimbal. The telescope has various modes of operation, including prime-focus, bent- and direct-Gregorian modes. The telescopes can feed independent instruments or their light can be combined in one of two interferometric instruments, giving an interferometric baseline of over 22 m. With all large telescopes, including the LBT, collimation models or modeled values for hexapod positions, are required to maintain reasonable optical alignment over the working range of temperatures and telescope elevations. Unlike other telescopes, the LBT has a highly asymmetric mechanical structure, and as a result the collimation models are required to do a lot more "work", than on an equivalent aperture monocular telescope that are usually designed to incorporate a Serurrier truss arrangement. LBT has been phasing in science operations over the last 5 years, with first light on the prime-focus cameras in 2006, and first light in Gregorian mode in 2008. In this time the generation of collimation models for LBT has proven to be problematic, with large departures from a given model, and large changes in pointing, being the norm. A refined approach to generating collimation models, "range balancing", has greatly improved this situation. The range-balancing approach to generating collimation models has delivered reliable collimation and pointing in both prime focus and Gregorian modes which has led to greatly increased operational efficiency. The details of the range-balancing approach, involving the removal of pointing "contamination" from collimation data, are given in this paper. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).


Miller D.L.,Binocular | Rakich A.,Binocular | Leibold T.,Binocular
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

A recent upgrade of the LBTO's Wavefront Reconstruction algorithm in the Active Optics system has proven to reduce the collimation time by a substantial amount and to provide a much more stable telescope collimation as observing conditions change. The new reconstruction algorithm uses Source Extractor to detect the spots in a Shack-Hartmann wavefront sensor camera image. With information about which Shack spots are detected, a reconstructor matrix is calculated on-the-fly that only includes the illuminated sub-apertures. This drastically improves the wavefront reconstruction for a highly aberrated wavefront when many sub-apertures contain no information. This is generally the situation at the beginning of the night when the collimation of the telescope is set only from models rather than on-sky information and occasionally when a new observational target is acquired. Similarly, the undersized tertiary mirror can cause vignetting of the pupil seen by the Shack-Hartmann wavefront sensor for far off-axis guide stars and again some sub-apertures have no wavefront information. We will present a brief description of the Active Optics system used at the Gregorian focal stations at the LBTO, discuss the original wavefront reconstruction algorithm, describe the new Source Extractor algorithm and compare the performance of these two approaches in several conditions (low signal to noise, highly aberrated wavefront, vignetted pupil, poor seeing). © 2012 SPIE.


Rakich A.,Binocular | Rakich A.,European Southern Observatory
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The Large Binocular Telescope (LBT) currently achieves collimation using a combination of collimation models and closed-loop active correction schemes. Shack Hartmann wavefront sensors with off-axis guide stars are used for Gregorian modes, and a closed-loop correction scheme is used for the prime-focus cameras. While in general this combination serves to produce alignment residuals well below a good seeing limit within a few minutes of obtaining a given target field, the uniquely asymmetrical structure of the LBT is prone to producing large deflections of the telescope optics when the ambient temperature is changing unusually rapidly. These deflections are difficult to model satisfactorily, and are an ongoing source of inefficiency in telescope operations. Furthermore, none of the current approaches to telescope collimation are particularly "piston aware"; a situation that needs to be improved on now that the LBT is commencing operations with the first of its beam combining instruments, LBTI. The laser tracker is a metrologyinstrument capable of automatically measuring optical element positions with better than 100 micron precision within a spherical volume of 30 m radius centered on the tracker head. With the ability to directly measure optics into position to this accuracy built into the Telescope Control System (TCS), the LBT would always be starting observations from a point of near-collimation, the component telescopes would be co-pointed, and the OPD would be well within the capture range of the beam combining instrument's internal phasing systems. This paper describes first results from engineering investigations into using the laser tracker to automatically align the optics on the LBT. © 2012 SPIE.


Wagner R.M.,Binocular
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

An overview of instrumentation for the Large Binocular Telescope is presented. Optical instrumentation includes the Large Binocular Camera (LBC), a pair of wide-field (27′ x 27′) mosaic CCD imagers at the prime focus, and the Multi-Object Double Spectrograph (MODS), a pair of dual-beam blue-red optimized long-slit spectrographs mounted at the straight-through F/15 Gregorian focus incorporating multiple slit masks for multi-object spectroscopy over a 6 field and spectral resolutions of up to 8000. Infrared instrumentation includes the LBT Near-IR Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (LUCIFER), a modular near-infrared (0.9-2.5 μm) imager and spectrograph pair mounted at a bent interior focal station and designed for seeing-limited (FOV: 4′ x 4′) imaging, long-slit spectroscopy, and multi-object spectroscopy utilizing cooled slit masks and diffraction limited (FOV: 0′.5 x 0′.5) imaging and long-slit spectroscopy. Strategic instruments under development for the remaining two combined focal stations include an interferometric cryogenic beam combiner with near-infrared and thermal-infrared instruments for Fizeau imaging and nulling interferometry (LBTI) and an optical bench near-infrared beam combiner utilizing multi-conjugate adaptive optics for high angular resolution and sensitivity (LINC-NIRVANA). In addition, a fiber-fed bench spectrograph (PEPSI) capable of ultra high resolution spectroscopy and spectropolarimetry (R = 40,000-300,000) will be available as a principal investigator instrument. The availability of all these instruments mounted simultaneously on the LBT permits unique science, flexible scheduling, and improved operational support. Over the past two years the LBC and the first LUCIFER instrument have been brought into routine scientific operation and MODS1 commissioning is set to begin in the fall of 2010. © 2010 Copyright SPIE - The International Society for Optical Engineering.


Rakich A.,Binocular
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The laser tracker allows the precise determination of positions of surfaces in three dimensions over volumes exceeding 30 m radius from the tracker head. At the Large Binocular Telescope a laser tracker has recently been employed for the initial alignment of all telescope optics in the right hand side (DX) bent Gregorian optical train. In this paper the particular approach to alignment of optical elements employed during this campaign is discussed in detail, together with results and expected accuracies. Subsequent to this "mechanical alignment" the telescope was taken "on-sky" and a subsequent "optical alignment" using a Shack-Hartman wavefront sensor with stellar sources took place. Ongoing activities include using the laser tracker to measure elevation and thermally induced displacements of individual optical elements. © 2010 SPIE.


Jainta S.,Binocular | Vernet V.,Binocular | Yang Y.,Binocular | Kapoula Z.,Binocular
Frontiers in Human Neuroscience | Year: 2011

The eye produces saccadic eye movements whose reaction times are perhaps the shortest in humans. Saccade latencies reflect ongoing cortical processing and, generally, shorter latencies are supposed to reflect advanced motor preparation. The dilation of the eye's pupil is reported to reflect cortical processing as well. Eight participants made saccades in a gap and overlap paradigm (in pure and mixed blocks), which we used in order to produce a variety of different saccade latencies. Saccades and pupil size were measured with the Eye Link II. The pattern in pupil dilation resembled that of a gap effect: for gap blocks, pupil dilations were larger compared to overlap blocks; mixing gap and overlap trials reduced the pupil dilation for gap trials thereby inducing a switching cost. Furthermore, saccade latencies across all tasks predicted the magnitude of pupil dilations post hoc: the longer the saccade latency the smaller the pupil dilation before the eye actually began to move. In accordance with observations for manual responses, we conclude that pupil dilations prior to saccade execution reflect advanced motor preparations and therefore provide valid indicator qualities for ongoing cortical processes. © 2011 Jainta, Vernet, Yang and Kapoula.


Loading Binocular collaborators
Loading Binocular collaborators