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    A new theory of complex rays
    (Oxford Univ Press, 2004-12) Hasanoğlu, Elman
    A new approach to the theory of complex rays is presented. It is shown that the three-dimensional Minkowski space, the variant of the well known four-dimensional space-time Minkowski space of the special theory of relativity, is more appropriate for describing both real and complex rays than the usual Euclidean space. It turns out that in this space complex rays, as real ones, may have quite definite directions and magnitudes. This allows us to understand the geometrical meaning of the complex magnitudes such as complex distances and complex angles, intensively discussed over the last several decades. From this point of view a new interpretation of the Gaussian beams and reflection laws is presented.
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    A flexible adaptive optics concept for general purpose high angular resolution science on the DAG 4m telescope
    (SPIE-Int Soc Optical Engineering, 2018) Jolissaint, Laurent; Bouxin, Audrey; Gökay, Ulaş Sabahattin; Keskin, Onur; Rigaut, Francois; Yeşilyaprak, Cahit
    Thanks to the availability of high actuator density deformable mirrors (ALPAO 468 DM), the high versatility of the pyramid wavefront sensor and above all, the venue of essentially no noise EMCCD detectors, it becomes possible to fully adapt the degree of correction of an adaptive optics system for a given guide star brightness and atmospheric condition. Indeed, when the conditions are very good, the high actuator density of the DM allows to reach a high Strehl by using all the modes, and when the conditions are less favorable, the spatial sampling, i. the number of modes, and the sensitivity of the detector allows to maximize the Strehl beyond what would be possible with a classical, frozen SH-WFS based system. Beside, oversampling the detector allows to relax the specification on the pupil images given by the pyramid on the detector, which in turn relaxes the pyramid prism manufacturing specifications. We are now designing an AO system for the DAG 4 m telescope that will allow, on the same system, ExAO as well as low order improved seeing observations. This article reports on the AO performance analysis, the final optical design and the design of the double prism achromatic pyramid.
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    TROIA Adaptive optics system for DAG telescope; assembly and laboratory performance prior to on-sky assessment
    (SPIE, 2022-08-29) Keskin, Onur; Jolissaint, Laurent; Bouxin, Audrey; Yeşilyaprak, Cahit
    In this article, we describe the current status of the development of TROIA* a pyramid wavefront sensor based adaptive optics system designed for DAG, a new 4 m telescope located in Eastern Anatolia, Turkey. The wavefront uses a no-noise electron-multiplied CCD camera, and the deformable mirror has a large actuators density, allowing coronagraphic science in one hand, but also system optimization for low light level or bad seeing conditions thanks to the versatility of the P-WFS. We describe the optical design, the mounting and alignment procedure and our loop control concept. Closed loop results are described, showing that while there are still many issues to fix before the sky version, the system behaves as expected.
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    Two reflector non symmetric shaped antenna systems
    (IEEE, 2000) Hasanoğlu, Elman
    Two reflector antenna systems with non symmetric reflecting surfaces under GO approximation are investigated. It is shown, that the problem of forming desired far field pattern leades to solving the system of partial differential equations with respect to mapping functions between wave fronts. One of these equations is non linear and expresses energy conversation law. It is shown that this equation can be solved separetly in the class of non smooth functions which has a discontinuty of first kind along a given curve.
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    The flexible adaptive optics concept
    (Instituto de Astrofisica de Canarias, 2017) Jolissaint, Laurent; Eikenberry, Stephen Steve; Bouxin, Audrey; Keskin, Onur; Yeşilyaprak, Cahit
    The availability of small deformable mirrors with large number of actuators and stroke, on one hand, and versatile wavefront sensors (pyramid WFS), on the other, allows the development of AO systems whose equivalent pitch can be adapted freely to the guide stars and seeing conditions. On moderately large telescopes (4 m class) this exibility allows a performance (Strehl and limiting magnitude) always better than what a classical, frozen Shack-Hartman design would allow. Moreover, adding several natural guide star wavefront sensors, we believe a single system could do anything from extreme AO to GLAO, i.e using the same hardware, and adapting the control software parameters to the observation mode. Taking advantage of such a system requires the use of a zoom optics in the imager in order to optimally match the plate scale with the PSF. We demonstrate that sub-optimal pixel size would result in a significant loss in term of science data reduction, in particular object detectability. The raison d'etre of such a versatile system is to popularize AO in community of astronomers not familiar with it, by allowing, on the same telescope, high resolution as well as seeing improved observations. This is particularly important for countries where very few large telescopes are available. On the long term, we think that most moderate size telescopes will have this sort of exible multi-purpose AO systems as a default. The exible AO concept will be implemented on the new 4 m Turkish telescope, DAG. © 2017 Instituto de Astrofisica de Canarias. All rights reserved.