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行星天象圖 Celestial phenomena 2025

 From NAOJ : HKT(UT+8) From HKO

朝鮮世宗期における 天文儀器の開発と利用

 Sang-Hyeon Ahn (韓國天文硏究院) 2020.12.05. @天文文化研究会 Political transition  高麗->朝鮮 朝鮮世宗  1397-1450 禮樂制度 The morality was well described by a sentence in a famous Chinese classic called lizi (禮記):  “大樂與天地同和. 大禮與天地同節,” which is translated as “Great music harmonizes with the Nature  Great rites follows the order of the Nature.” Here the concept of harmonization is related with politics, and that was realized or demonstrated by ancestral rites 祭祀. Music is an important part in performing rituals 儀式. Music can unite people! Moreover, the concept of the order of Nature is realized by an exact definition of seasonal grants 節氣 that is calendar. Calendar can give public order to the people! 渾儀,渾象,簡儀,小簡儀 日星定時儀: Its structure consists of three rings on a cross, called the Jucheondo-bunhwan (周天度分環), Ilgubaekgak-hwan (日晷百刻環), and Seonggubaekgak-hwan (星晷百刻環), and it is made based on the altitude (latitude) of the North Pole in Hanyang. The north and south are ruled by aligning th...

How to choose electronic balance and how to check accuracy

Funny calibration guide from timemore: No of bits of ADC is more important Usually it's 24 bits eg in HX711,  looks like this 24 bit ADC will give about 14 to 15 noise-free bits.  ie range is say 2^14 to 2^15 usable. Arduino forum   Eg a 0.01g minimum gradation  The range is theoretically 0.01 to 163.84g, or 327.68g  so if it can measure up to 200g, the repeatability in this range is pretty safe. Min grad can be misleading  起稱範圍 is more important  See reply below: Eg this Balance claimed a 0.001g (1mg) But initial is 0.005g If possible, choose one with one more decimal digit. Eg if you want to measure up to 0.01g, choose one that displays 0.001g Btw, those cheap balance( under¥100), most can only repeatedly measure up to 0.01g, even it says 0.001g accuracy  The weight 砝碼 provided with the kit is usually 100g ,M grade. This is pretty meaningless(~¥7) But if you want to measure 0.1g or less, better to use at least F2 grade weight Hysteresis of load ...

Carlsberg group and lager beer

Contributions Inventing pH scale(1909) purifying lager yeast (1883) at Carlsberg laboratory, Emil C. Hansen, discovered a method of isolating yeast so that brewers could use fresh yeast during every fermentation. This yeast was named as Saccharomyces Carlsbergensis and it was distributed freely to anyone including other brewers until 1988.  Role of  enzymes  Malt roasting Reference  Carlsberg group   Ontario  pressbook

Astrolabe with geared calendar

Muhammad Ibn Abi Bakr, Isfahan 1221/2 AD Front: Back: Composite: Composite back: Drawing: Reference  HSM UK