tailieunhanh - The 50 cm telescope of Hoa Lac observatory: An introduction

The Vietnam National Space Center has recently established an observatory in Hoa Lac, near Ha Noi. The observatory is equipped with a 50 cm diameter Ritchey-Chrétien optical telescope. The authors report on first measurements illustrating its performance and demonstrate its excellence as a training tool for university students at bachelor’s and master’s degree levels. | PHYSICAL SCIENCES PHYSICS Doi 4 .14-28 The 50 cm telescope of Hoa Lac observatory an introduction Nguyen Thi Thao1 2 Mai Thuy Dung1 Pham Vu Loc1 Nguyen Thi Kim Ha1 Pham Ngoc Diep1 and Pierre Darriulat1 Department of Astrophysics Vietnam National Space Center Vietnam Academy of Science and Technology 2Graduate University of Science and Technology Vietnam Academy of Science and Technology Received 20 September 2019 accepted 12 November 2019 Abstract The Vietnam National Space Center has recently established an observatory in Hoa Lac near Ha Noi. The observatory is equipped with a 50 cm diameter Ritchey-Chrétien optical telescope. The authors report on first measurements illustrating its performance and demonstrate its excellence as a training tool for university students at bachelor s and master s degree levels. Keywords astronomy CCD camera telescope. Classification number 1. Description of the telescope The Hoa Lac observatory 105 32 31 E 21 01 07 N near sea level of the Vietnam National Space Center VNSC was commissioned in June 2018. It hosts a 50 cm f 8 Ritchey-Chrétien reflecting telescope 1 equipped with a CCD array in the focal plane. Fig. 1 displays photographs of the observatory and of the telescope. A similar telescope equips the Nha Trang VNSC observatory in Hon Chong. Here we report on measurements illustrating the performance of the former. . Optics The telescope is of the Ritchey-Chrétien type a variant of the Cassegrain design. It includes a primary mirror which reflects the light onto a smaller coaxial secondary mirror. The secondary mirror produces the image on the focal plane located behind the primary mirror and then the light beam passes through the small central hole of the primary mirror Fig. 2 . The Ritchey-Chrétien design uses hyperbolic mirrors aimed at suppressing off-axis optical errors such as coma and spherical aberration but it introduces some Fig. 1. Left the Hoa Lac observatory telescope installed in the dome