Browsing by Author "Gadey, Nishant Neeraj"

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    An alternative, versatile, high†tolerance design of a modified Richter–Slevogt camera, using standard glasses /
    (John Wiley & Sons, 2024-02-06) Gadey, Nishant Neeraj
    Prime-focus catadioptric astrographs have been used for a long time in various astronomical applications. The prime advantage offered by them is the capability to produce remarkably wide fields of view, and hence generate a huge amount of data in relatively less observation time. An emerging application of such wide-field astrographs is in the form of telescope arrays. While this has been implemented mostly, using commercial refractive lenses, low-cost catadioptric objectives can be used as an alternative for wide-field or high-contrast array applications. Commercial catadioptric systems are generally available as modifications of Schmidt and Maksutov systems, that too, mostly in the Cassegrain configuration. Here, we present a low-cost alternative prime focus camera design of Richter–Slevogt configuration, which is in turn an extension of the Houghton correctors. The Richter–Slevogt design has the potential for a very high performance due to several degrees of freedom. The presented one is a 150 mm aperture, system, providing 3.5° (circular) diffraction-limited FOV (strehl ), using only standard glasses, N-BK7 and F2. We present the performance analysis, tolerance sensitivity, and statistical (Monte-Carlo) analysis for this design. Potential applications of the system, other than as an array are also briefly discussed.
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    Mersenne beam-compressor with field-flattener optics as main telescope design for extremely large telescopes and telescope arrays /
    (World Scientific Publishing Co Pte Ltd, 2022-02-04) Gadey, Nishant Neeraj
    The Mersenne beam-compressor is the fundamental arrangement for two mirror reflecting telescopes. The Mersenne beam-compressor consists of two confocal paraboloids. The design produces an aberration-free, collimated output beam, which makes it easy to relocate the beam to any distant location. This property of Mersenne beam compressors makes them near-ideal for telescopes with requirements for ultra-stable instruments and interferometric applications. The only problem against such application is the Petzval field curvature that is induced in the output beam. This becomes very pronounced at very high compression ratios, which are required for interferometry with large aperture telescopes. The high compression ratio is a problem because, such large aperture telescopes are also required to deliver good performance at Nasmyth and Coude locations, to be feasible. This is not possible at high compression ratios using conventional design of Mersenne beam-compressor, due to prohibitively strong field curvature. Here, we propose powered and un-powered field-flattener optics to address the problem of field curvature in Mersenne beam-compressor. After passing through this set of optics, the output beam is completely aberration free. This arrangement can produce very high compression ratios, which are useful for various special applications. We also illustrate the performance of such a system using example designs. The performance analysis shows that such a design can give considerably high performance at distant locations of foci as compared to existing relay systems.