The 50 cm telescope of Hoa Lac observatory: an introduction

Thảo, Nguyễn Thị Phương; Dung, Mai Thuy; Loc, Pham Vu; Hà, Nguyễn Thị Kim; Diep, P. N.; Darriulat, Pierre

doi:10.31276/vjste.61(4).14-28

Cited by 2 publications

(1 citation statement)

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“…Nha Trang and Hoa Lac astronomical observatories are located in the subtropical belt near sea level. Both observatories belong to the Vietnam National Space Center and are equipped with modern 50 cm Ritchie-Chrétien telescopes [18].…”

Section: Introductionmentioning

confidence: 99%

Astroclimatic Conditions at the Hoa Lac and Nha Trang Astronomical Observatories

et al. 2021

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The paper presents the first results of astroclimatic studies at the sites of the Hoa Lac and Nha Trang astronomical observatories. Our study employs Era-5 data covering a 10-yr time period (2011–2020). An analysis of the main astroclimatic characteristic, namely, the wind speed in the upper layers of the atmosphere, was performed. We calculated space distributions of the wind speed averaged in the height bin from 100 to 200 hPa. Using hourly data on pressure levels we analyzed probability distributions of the wind speed at high-level maxima at the sites of the observatories. At the Nha Trang observatory the period with a potentially high astroclimatic conditions falls on the spring when high recurrence of weak winds is observed. At the Hoa Lac observatory the best conditions are observed in the summer and the autumn. In this period, the median wind speeds are low. Additionally, we calculated spectra of the air temperature using the Fast Fourier Transform. We analyzed the deformations of the spectra with heights in a wide range of scales. At the site of the Nha Trang Astronomical Observatory, the amplitude of daily air temperature variations in the surface layer is approximately 1.5–2.5 times smaller compared to the Hoa Lac Observatory. We showed that the low-frequency maximum in the spectra is pronounced only in the lower layers of the atmosphere.

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Section: Introductionmentioning

confidence: 99%

Astroclimatic Conditions at the Hoa Lac and Nha Trang Astronomical Observatories

et al. 2021

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Interferometric Method to Control the Convex Aspherical Surface Shape using a Concentric Meniscus Lens

Nguyen

Druzhin

2023

HoBMSTU.SIE

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Convex aspherical surfaces are being increasingly used as elements of the high-precision optical devices for various purposes. Complexity in such surfaces manufacture is because the existing methods of their shape control with the optical accuracy of about 20--30 nm require introduction of the auxiliary reference optical elements, which dimensions are several times larger than those of the controlled part are. The paper proposes the autocollimation control method using a concentric meniscus lens with dimensions slightly exceeding the dimensions of the controlled part. Results of calculating the control circuit design parameters are presented based on the theory of the third-order aberrations. Effect of the refractive index and thickness of a concentric meniscus lens on the maximum and root-mean-square deviations of the surface shape with various requirements to concentric meniscus lens radii was considered, and the developed scheme simulation in the Zemax soft-ware was also proposed. The Fizeau interferometer optical scheme was described using a lens with the reference surface to implement the developed method. Applied research was carried out to control the secondary mirrors of the Ritchie --- Chretien telescope at the Hoa Lak Observatory (Vietnam) and of the SNAP satellite telescope

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The 50 cm telescope of Hoa Lac observatory: an introduction

Cited by 2 publications

References 0 publications

Astroclimatic Conditions at the Hoa Lac and Nha Trang Astronomical Observatories

Astroclimatic Conditions at the Hoa Lac and Nha Trang Astronomical Observatories

Interferometric Method to Control the Convex Aspherical Surface Shape using a Concentric Meniscus Lens

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