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Image formation with partially coherent radiation is evaluated with the Hopkins formula and then applied to x-ray microscopy. Image characteristics expected from instruments with circular and annular pupils in partially coherent conditions are considered for two-point objects and a knife-edge object. The theoretically expected values for image characteristics that are easy accessible by an experiment, such as the width of a knife edge, are given for various x-ray microscopes.

The conceptual design of the Gran Telescopio Canarias (GTC) has been completed. One of the challenges facing the GTC Project is to obtain excellent image quality using a segmented primary mirror. The segmentation will introduce a physical effect that contributes to significant degradation of image quality.The image quality requirement imposes the use of an active optical system to correct figure instabilities of the optical surfaces and part of the unavoidable fabrication figure errors. The active correction includes the capability of 5-axis motion of the secondary mirror, 3-axis motion of each primary mirror segment, and 6 active degrees of freedom to deform each segment. A mixed strategy of closed-and open-loop control of the active correction will be implemented. This paper discusses the expected wavefront errors of the GTC, how they are corrected by active optics, and the expected image quality performance in FWHM, 080 and Central Intensity ratio.

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The Gran Telescopio Canarias (GTC) is a lOm-class telescope which is under construction and will be operational at the Observatorio del Roque de Los Muchachos at the end of 2003. The goal of this paper is to describe the current status of the design and construction of the primary, secondary and tertiary mirrors of the GTC and their opto-mechanical supports. It also summarizes the optical performances expected from the GTC and the error budget of the optical system.The primary mirror is segmented into 36 hexagonal segments. Each segment can be actively deformed to correct figure distortion. In addition, an active stabilization ioop permits the relative position between the segments to be maintained so that they will function as a single optical surface. The GTC will work with a single secondary mirror, which will be used for both visible and infrared observations. Only the system of baffles will be changed between observations in he visible and infrared. The secondary mirror will be a lightweight glass mirror moved by a driving unit with the capability of active alignment and fast tip-tilt correction; the latter function will be used for chopping and image motion correction. The tertiary mirror will permit the light beam to be directed to the Nasmyth and folded-Cassegrain focal stations. A trade-off of several alternatives that we have evaluated will be presented as well the current concept for the mirror and the support.

In this work, it is described the Imaging Magnetograph eXperiment, IMaX, one of the three postfocal instruments of the Sunrise mission. The Sunrise project consists on a stratospheric balloon with a 1 m aperture telescope, which will fly from the Antarctica within the NASA Long Duration Balloon Program.IMaX will provide vector magnetograms of the solar surface with a spatial resolution of 70 m. This data is relevant for understanding how the magnetic fields emerge in the solar surface, how they couple the photospheric base with the million degrees of temperature of the solar corona and which are the processes that are responsible of the generation of such an immense temperatures.To meet this goal IMaX should work as a high sensitivity polarimeter, high resolution spectrometer and a near diffraction limited imager. Liquid Crystal Variable Retarders will be used as polarization modulators taking advantage of the optical retardation induced by application of low electric fields and avoiding mechanical mechanisms. Therefore, the interest of these devices for aerospace applications is envisaged. The spectral resolution required will be achieved by using a LiNbO 3 Fabry-Perot etalon in double pass configuration as spectral filter before the two CCDs detectors. As well phase-diversity techniques will be implemented in order to improve the image quality.Nowadays, IMaX project is in the detailed design phase before fabrication, integration, assembly and verification. This paper briefly describes the current status of the instrument and the technical solutions developed to fulfil the scientific requirements.

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