On the design of wide-field x-ray telescopes
X-ray telescopes having a relatively wide field-of-view and spatial resolution vs. polar off-axis angle curves much flatter than the parabolic dependence characteristic of Wolter I designs are of great interest for surveys of the X-ray sky and potentially for study of the Sun's X-ray emission. We discuss the various considerations affecting the design of such telescopes, including the possible use of polynomial mirror surface prescriptions, a method of optimizing the polynomial coefficients, scaling laws for mirror segment length vs. intersection radius, the loss of on-axis spatial resolution, and the positioning of focal plane detectors.
Optimization of grazing incidence mirrors and its application to surveying X-ray telescopes
Grazing incidence mirrors for X{ray astronomy are usually designed in the parabola-hyperbola (Wolter I) conguration. This design allows for optimal images on-axis, which however degrade rapidly with the o-axis angle. Mirror surfaces described by polynomia (with terms higher than order two), have been put forward to improve the performances over the eld of view. Here we present a rened procedure aimed at optimiz- ing wide-eld grazing incidence telescopes for X{ray astronomy. We improve the angular resolution over existing (wide-eld) designs by 20%. We further consider the corrections for the dierent plate scale and focal plane curvature of the mirror shells, which sharpen by another20% the image quality. This results in a factor of2 reduction in the observing time needed to achieve the same sensitivity over existing wide-eld designs and of5 over Wolter I telescopes. We demonstrate that such wide-eld X{ray telescopes are highly advantageous for deep surveys of the X{ray sky.
Optical rotatory dispersion and absolute configuration—III
Abstract Optical rotatory dispersion measurements on pyrrolidine, piperidine, and tetrahydro-isoquinoline alkaloids indicate that the absolute configuration of the α-asymmetric center may be assigned directly from the dispersion curve, provided either that the nitrogen atom is not protonated, or that the compound contains a chromophore absorbing above 200 mμ.