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Yayın The design of an adaptive optics telescope: the case of DAG(SPIE, 2016-07-27) Jolissaint, Laurent; Keskin, Onur; Zago, Lorenzo; Yerli, Sinan Kaan; Yeşilyaprak, Cahit; Mudry, Emeric; Lousberg, Grégory P.In this paper, we describe in detail the optical design of DAG, a new 4 m telescope for Turkey. DAG is an "adaptive optics friendly" telescope, in a sense that each design decision is taken considering the potential impact on the AO performance (vibrations, static aberrations etc.) The objective is to make this telescope fully ready for AO at first light. It is designed as a Ritchey-Chretien combination, 56 m focal length, with Nasmyth foci only, and active optics. Its total RMS error is expected to be 45 nm up to Zernike mode 78, and 26 nm for the higher, non AO corrected modes. A final design optimization has been done by the telescope manufacturers, demonstrating that our AO-based requirements can be satisfied, without much difficulty.Yayın DAG 4m telescope: assembly, integration and testing(SPIE-Int Soc Optical Engineering, 2018-07-06) Pirnay, Olivier; Lousberg, Grégory P.; Gabriel, Eric; Marchiori, Gianpietro; Busatta, Andrea; Yeşilyaprak, Cahit; Keskin, OnurAMOS with EIE as a main subcontractor, was awarded a contract in November 2014 for the design, manufacturing and installation of a 4m-class telescope for the Turkish Eastern Anatolia Observatory (DAG) situated at 3170 m above the sea level in Palandöken mountains. The telescope is based on a Ritchey-Chretien configuration with two folded Nasmyth focal planes and a focal length of 56m. Diffraction-limited performances will be reached thanks to the combination of the active optics system and the adaptive optics system that will be implemented on one of the Nasmyth ports. The active optics system aims at controlling the shape of the primary mirror by means of 66 axial force actuators and positioning actively the secondary and tertiary mirrors by means of hexapods. More than 30 years of experience in testing instruments and telescopes, including optical testing, alignment, metrology, mechanical static and dynamic measurements, system identification, etc. allow to implement an adequate verification strategy combining component level verifications with factory and site test in the most efficient and reliable manner. As a main contractor, AMOS is in charge of the overall project management, the system engineering, the optical design and the active optics development. As a main sub-contractor and partner of AMOS, EIE is in charge of the development of the mount. The factory test therefore takes place in EIE premises. In this paper is shortly presented the overall design of the telescope with a review of the specification, the optical design and a description of the major sub-systems, including the optics. The assembly, integration et test plan is outlined. The assembly sequence and the tests of the active optics and the mount are discussed. Finally, the site integration and tests are explained. The process to assess the image quality of the telescope and the verification instrument developed for this purpose by AMOS are presented.Yayın Eastern Anatolia Observatory (DAG): Recent developments 2017(SPIE-INT Soc Optical Engineering, 2018-07-06) Yeşilyaprak, Cahit; Keskin, OnurEast Anatolia Observatory (DAG) is the new observatory of Turkey with the optical (VIS) and near-infrared (NIR) largest telescope (4 m mirror) and its robust observing site infrastructure. This national project consists of three phases with DAG (telescope, enclosure, building, infrastructure), FPI (Focal Plane Instruments and Adaptive Optics) and MCP (Mirror Coating Plant) and is supported by the Ministry of Development of Turkey. Almost all infrastructure (roads, geological and atmospheric surveys, electricity, fiber optics, water, generator, etc.) of DAG site (Erzurum/Turkey, 3170 m altitude) have been completed. The recent developments (telescope, enclosure, mirror, focal plane instruments, building, atmospheric studies, etc.) of DAG and its site in 2017 and 2018 were presented for the future possible collaborations for various astronomical instruments and telescopes which can be set up in DAG site.Yayın The DAG Project, a 4m class telescope: The telescope main structure performance(SPIE, 2016) Marchiori, Gianpietro; Busatta, Andrea; Ghedin, L.; Marcuzzi, Enrico; Manfrin, Cristiana; Battistel, C.; Pirnay, Olivier; Flebus, Carlo; Yeşilyaprak, Cahit; Keskin, Onur; Yerli, Sinan KaanDogu Anatolu Gözlemevi (DAG-Eastern Anatolia Observatory) Project is a 4m class optical, near-infrared Telescope and suitable enclosure which will be located at an altitude of 3.170m in Erzurum, Turkey. The DAG telescope is a project fully funded by Turkish Ministry of Development and the Atatürk University of Astrophysics Research Telescope - ATASAM. The Project is being developed by the Belgian company AMOS (project leader), which is also the optics supplier and EIE GROUP, the Telescope Main Structure supplier and responsible for the final site integration. The design of the Telescope Main Structure fits in the EIE TBO Program which aims at developing a Dome/Telescope systemic optimization process for both performances and competitive costs based on previous project commitments like NTT, VLT, VST and ASTRI. The optical Configuration of the DAG Telescope is a Ritchey-Chretien with two Nasmyth foci and a 4m primary thin mirror controlled in shape and position by an Active Optic System. The main characteristics of the Telescope Main Structure are an Altitude-Azimuth light and rigid structure system with Direct Drive Systems for both axis, AZ Hydrostatic Bearing System and Altitude standard bearing system; both axes are equipped with Tape Encoder System. An innovative Control System characterizes the telescope performance.Yayın Eastern Anatolia Observatory (DAG): The status in 2020(SPIE, 2020) Yeşilyaprak, Cahit; Keskin, OnurEast Anatolian Observatory's DAG telescope, with its 4m diameter primary mirror and VIS/IR observation capability, will be located on the Konakll-Karaya summit at an altitude of 3170 m, near the city of Erzurum, Turkey. Containing both active optics (aO) and adaptive optics (AO) systems, the first light for DAG is expected for the last quarter of 2021. DAG will be equipped with an in-flange derotator - KORAY (K-mirror Optical relAY) that will direct the light to the seeing limited Nasmyth platform containing TROIA (TuRkish adaptive Optics system for Infrared Astronomy). DAG first generation instruments will consist in a 30"FoV near-infrared (NIR) diffraction limited camera and a stellar coronagraph. In his paper, status updates from DAG telescope will be presented in terms of; (i) DAG site, (ii) Site infrastructure, (iii) current status of the observatory building, (iv) DAG optics, (v) current status of the telescope, (vi) current status of enclosure, (vi) current progress of the astronomical instruments, and (viii) status of the Optomechatronics Research Laboratory - OPAL.Yayın Advances for the 4m DAG Telescope in Flange derotator(SPIE, 2020-12-13) Keskin, Onur; Ünal, Ali Cem; Koç, İlker Murat; Jolissaint, Laurent; Yeşilyaprak, CahitThe purpose of this study is expressing advances in design stages for in flange optical field derotator system for 4 meters DAG Telescope. In-Flange Derotator KORAY (K-mirror OpticalRelAY) is designed, analysed and manufactured to meet the specifications of DAG telescope. DAG telescope, situated at Erzurum/Karakaya summit at 3150m altitude, is the first Turkish optical telescope with VIS(Visible) and IR (Infrared) observation capability. DAG, designed by Turkish engineers at FMV Isik University, is also the largest telescope (4m diameter) in Turkey and in European continent. Being one of the 2023 vision projects; the first light of DAG is expected to take place in 2021. This purpose brings some real-life challenges such as design limitations, material selection and electronic integration.
