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Stargazing facility in Sai Wan, Sai Kung

Sai Kung has always been a hot spot for the public to stargaze. The Government has constructed a stargazing facility on an abandoned campsite located between Sai Wan and Ham Tin Wan in Sai Kung for visitors to enjoy stargazing by lying down leisurely and comfortably. (Other Astronomical Observation Hot Spots/Weather Information) The stargazing facility is situated on a small knoll. Walking along the MacLehose Trail Section 2 from Sai Wan Beach uphill for about 10 minutes, you will see the “Sai Wan Stargazing Site” sign. Reconstructed from a campsite The newly constructed stargazing facility is a curved ring-form bench composed of glass reinforced resin panels, which are hard, durable and suitable for outdoor use. The bench, which is built with great respect for the surrounding tree line, beautifully blends the streamlined design into nature. Architect of the ArchSD, Mr LO Yee-cheung, Adrian, says the location was originally an abandoned campsite with a piece of spacious flat land. The reconstruction works did not involve tree felling, which minimised ecological and visual impacts. The bench with ergonomic design Adrian shares that the AFCD, Hong Kong Space Museum and ArchSD joined hands to explore the design of the stargazing facility and the construction commenced in October 2018. The most prominent feature of the project is the curved ring-form bench which allows 360-degree stargazing. People can view the starry sky no matter where they sit. The bench is ergonomically-designed so that people can enjoy stargazing by sitting in the most comfortable position at 135 degrees, which is more comfortable than lying on the ground. With its light timber colour as well as reflective coating on its top and bottom tips, the bench enables visitors to see it clearly even without artificial illumination so as to ensure safety. Adopting green and environmentally-friendly design Moreover, the central part of the stargazing facility is a hard-paved flat area for stargazers to set up their tripods and telescopes. Metal coordinate indicators are embedded in the ground to facilitate visitors to orient themselves and to appreciate the starry sky in different directions. Meanwhile, the project has adopted green and environmentally-friendly design to conserve the natural environment of the countryside. For example, pebbles are placed under the back of the bench to facilitate natural drainage without the need to lay any drains, and grasses fit for wild cows’ consumption are grown without the need to carry out grass cutting work manually or mechanically; as a result, symbiosis of human, nature and architecture can be achieved. (For more details, please click here to read the article in Development Bureau website)

Why do stars twinkle?

Since no astronaut while traveling in space has reported seeing stars twinkling, the effect must be atmospheric, i.e. due to air. However, it is not exactly correct to say that it is due to turbulence in the air.Mere turbulence in the air is just what we call wind. Wind does not make stars twinkle, because light travels at a great speed --- over 1 billion km/h.What distorts the light coming from a star is temperature variations in the air. As you probably know already, air temperature varies a great deal. It typically decreases by 6.5 degrees Celsius for every kilometre you go up, and this accords with the experience that it feels cooler up in the mountains. Also, on a hot day, you may notice the shimmering waves (thermals) that come off a heated road and make a distant car appear wavy.But exactly how do temperature variations cause twinkling?When light enters a transparent medium, such as air, it generally changes direction, i.e. it is scattered. By how much it changes direction, i.e. bent, however, depends on the temperature.Now any star, except the sun, is so far away that practically, it is sending only a single ray of light towards us. As that ray enters the atmosphere, it is scattered differently as it passes through air of different temperatures. When it is scattered away from us, the star seems to disappear for a moment. When it is scattered into our eyes, it seems to reappear, resulting in a twinkle.For more details, please click here to read the article written by Hong Kong Observatory. (Information provided by Hong Kong Observatory)