MENGUKUR ABERASI ASTIGMATISMA PADA TELESKOP RIFAST 500 F/3.8 MENGGUNAKAN METODE GEOMETRI
Abstract
Saat ini teleskop Ritchey-Chretien menjadi pilihan banyak astronom dalam melakukan pengamatan. Teleskop Ritchey-Chretien merupakan jenis teleskop reflektor yang mampu mereduksi aberasi koma dan sferis pada citra yang dihasilkan, namun aberasi astigmatisma masih dapat ditemukan pada teleskop ini. Penelitian ini akan membahas pengukuran astigmatisma dengan metode geometri pada citra yang dihasilkan oleh teleskop RiFast 500 f/3.8, yaitu teleskop Ritchey-Chretien dengan diameter 500 mm dan fokus 1900 mm. Luna et al. [7] menganggap metode geometri sebagai metode yang cukup sederhana untuk mengukur astigmatisma pada teleskop karena tidak memerlukan instrumen tambahan serta memiliki hasil yang sebanding dengan tes wavefront. Metode ini didasarkan pada pengukuran kontur elips yang dihasilkan oleh citra bintang yang tidak fokus star [7]. Pada penelitian ini diperoleh dua nilai astigmatisma pada dua posisi koordinat berbeda senilai 258.78 nm dan 300.39 nm.
Currently the Ritchey-Chretien telescope is the choice of many astronomers for their observations. The Ritchey-Chretien Telescope is a reflector telescope capable to reduce comma and spherical aberrations in the resulting image, but the aberration of astigmatism still be found on this telescope. The research is about measuring astigmatism aberration on RiFast 500 f/3.8 using geometric method, that is the Ritchey-Chretien telescope with diameter of 500 mm and focus of 1900 mm. Luna et al. [7] consider geometry methods is simple method for measuring astigmatism on telescopes because do not require additional instruments and the results is comparable with wavefront tests. This method is based the geometric analysis of the external contour of the image of a slightly defocused star [7]. In this study two astigmatism values were obtained at two different coordinate positions valued at 258.78 nm and 300.39 nm.
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