In order to measure the longitude difference between two distant sites, Inoh Tadataka and his technical team observed three lunar eclipses when surveying the Japanese Islands at the beginning of the 19^th century, and left some observation records. The local times when the partial eclipses began and ended were measured with a pendulum clock. By introducing the equation of time to the calendar date of the observations, the time difference can be obtained between the local time observed by Inoh and the lunar eclipse timetable of NASA shown in Japanese Standard Time at 135E degrees of longitude. Consequently, the accuracy of the longitude survey performed by Inoh Tadataka is evaluated in comparison to the precise map of the Geographical Survey Institute.

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Man-nen-dokei, which is a historic perpetual chronometer, was made by Hisashige TANAKA at 1851. It is said that Man-nen Dokei is one of best works in "wa-dokei", Japanese traditional clock. Recently, it has been disassembled and restored in a national project, so we investigated the mechanism of the Man-nen-dokei in cooperation with the project. This paper shows the mechanism of the celestial globe at the top face of Man-nen-dokei. Especially, we focus on (1) the mechanism for simulating the motion of the sun and the moon throughout the year, (2) the relationship between the definition of "mutsu" and the "shinkon-sai" in the celestial globe.

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 Land-survey expeditions across the Japanese archipelago during the period from 1800 to 1817 and scientific map-making conducted by Inoh Tadataka were monumental achievements in the Japanese history of cartography. How Inoh's astronomical knowledge and skills are reflected in his survey instrumentation and map fabrication of the Japan islands is reviewed. The contents of this paper are as follows: Section II makes an overview of Inoh's astronomical background nurtured both in his early life and at the Asakusa shogunal astronomical office; Sections III and IV discuss the influence of imported Chinese and Dutch books and European astronomical instruments on the survey apparatus used in the above expeditions; Section V describes his concrete star observation methods for determining local latitude, which were drawn by a local painter in the Kure district of Hiroshima in 1806; Section VI introduces survey work and map-making of the Sanuki fief in Shikoku by Kume Michikata, a surveyor and contemporary of Inoh, in contrast to those adopted by Inoh; and, Section VII comments on Inoh's cartographic policy and techniques in completing his famous Dainihon Enkai Yochi Zenzu (The Great Coastal Map of Japan).

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In 1872 the Meiji Government adopted the solar calendar, the twenty-four hours system and the new date, and in 1886 decided the Japanese Standard Time based on the time of the meridian of 135°E., running through Akashi in Hyôgo Prefecture near Kobe. Since then, the date and the time have entirely changed from those of the Edo period when the lunar-solar calendar and many local times prevailed throughout Japan.
The conversion of the old date into the new one is not so difficult task, but on the contrary, that of the old times into the new ones has complicated problems, because the old calendar system was different in many respects from the new one and also each clan adopted the local time derived from the time of each castle-town.
Firstly, the structure of the old calendar, which was introduced from China, was basically different from the new one. The length of the hour-units of daytime and nighttime differed according to the twenty-four short seasonal unit days, including the day of autumnal equinox, of vernal equinox, of summer solstice and of winter solstice. The beginning hours of daytime and nighttime were partly improved by the astronomers of the Tokugawa Government ; in the early part of the Edo period they were the times of sunrise and sunset of the castle-towns, and later they were more improved.
However, in 1797 TAKAHASHI-Yoshitoki, a young but an excellent astronomer, who studied the Western astronomy through the books edited by the European missionaries stationed in China and brought up INÔ-Tadataka, the greatest land-surveyor in the Edo period with the aid of astronomical observation, decided the times scientifically. He got the accurate position of the sun by spherical trigonometrical calculation, and cleared up the beginning and the end of twilight by the angle of depression of the center of the sun on the days of autumnal and vernal equinox at Kyoto the result was 7°21′40″. The new definition had been used until 1871.
This paper deals with some ways of conversion of the old times into the new ones, and illustrated, taking outstanding examples of castle-towns in the Edo period, how the converted times were different from one another throughout Japan in accordance with the latitudes and the longitudes of the towns.

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１．はじめに

　本報告では、伊能忠敬とも昵懇であった和算家・会田安明(1747-1817)が残した天文学に関する小品『天文簡要論』(1802年頃)を紹介する。本史料には、伊能が第3回測量までの間に測定したデータに基づき、会田に直接提供されたと考えられる情報や測量データが随所に盛り込まれている。20年余に及ぶ伊能の測量事業のほぼ初期に該当する年代に記され、伊能の同時代人による証言を留める史料として『天文簡要論』は貴重である。この観点から、『天文簡要論』が伊能忠敬について言及する内容を中心に紹介する。

２．『天文簡要論』が記す伊能忠敬由来の情報について

　本報告で紹介をする会田の『天文簡要論』は、天文暦学の基本的概念や歴史、雑録的な内容を上下2冊にまとめた写本である。日本学士院、東北大学附属図書館狩野文庫、山形大学小白川図書館佐久間文庫に所蔵が確認される。『天文簡要論』の上冊では過去の天文暦学者たちが残した成果の問題点を指摘、解説し、下冊ではそれらを乗り越えた最新の知見が披露される。伊能忠敬に関する記載は、最新の知見を示す事例として下冊に登場する。以下、その概要を掲出する。

　(1)伊能の測量術について

　｢地球大小論｣という項目で会田は、伊能忠敬による測量の目的、緯度１^°の距離(28.2里)、測量の技法の概要について言及する。伊能の測量法を示した史料としては従来、渡辺慎『東河先生流量地伝習録』が知られていたが、会田の叙述は簡単ながら、これと類似の内容を含んでおり、伊能の測量事業の初期の技法の一端をうかがうことができる。

　(2)北極星の高度と太陽の南中高度の測定について

「予カ勾陣大星ノ測量」「十七日夜勾陣大星ノ一測量」「同十七日立表測量」の項目において会田は、伊能宅において北極星の高度と太陽の南中高度を測定したことを記す(1798年12月23日のこと)。伊能宅に設置されていた天文観測器具を会田は自ら操作しており、『

書』に描かれている同様の器具類の実際の用法を知る上での参考となる情報が記されている。 　　

　(3)山形城下での観測データ

　｢羽州山形測量｣の項目において、第3次測量の際に伊能隊が通過した山形城下での天文観測記録を会田は記録に留めている。この記録の中に、どの恒星を観測したのかが略記されている。

　(4)山岳の標高に関するデータ

　「諸国山高測量」の項目で、会田は12箇所の山岳(月山、赤城山、磐梯山、岩木山、鳥海山、他)の標高を記している。伊能から会田に提供されたデータは象限儀で計測した山頂を見通した際の仰角であった。これらの数値は、伊能が測量した山岳に関わるデータを集成した史料『山島方位記』（現存67 冊）には記載されていないものである。会田はこれら仰角のデータと、伊能測量隊が作成した地図上での２地点間の距離、そして三角比を用いて標高(正確には標高差)を算出している。この計算を行うために、会田は伊能図に実際に物差しを当てて長さを測っていたことが記されている。

　(5)垂揺球儀の概要について

　｢垂揺球儀｣の項目において、伊能が計時のために用いた振り子時計「垂揺球儀」の概説をまとめる。会田は、この時計の発明者として間重富と高橋至時の2名を挙げている。

３．おわりに

　『天文簡要論』下冊から明らかになった事柄は以下のようになる。

・会田が伊能宅で天文観測を体験していたこと。

・伊能が第3 回測量旅行中に測定したデータ類を、会田は提供されていたこと。さらに伊能図も実見していたことがうかがえる。

・提供されたデータの中には、山頂を見通した仰角の測定値が含まれており、これらは既存の史料には確認できないものである。

・垂揺球儀の概要を記していること。

　伊能忠敬の同時代人が伊能の動向について書き残した史料は、書簡を中心として数多く残されている。しかし、間重富や高橋至時のように非常に近い関係にあった数人の天文暦学者を例外として、伊能の測量や天文観測の実態を的確な知識に基づいて記録をした史料は思いの外少ない。その観点から、会田安明の『天文簡要論』下冊は小篇でありながら、伊能の天文暦学、測量の実践に関する情報を現在に残す史料として位置づけられる。

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The surveying method used by Ino is called as “Dosen-Ho”，a kind of open traverse method. “Dosen”，that is to say，surveyed polygonal lines along coasts and main roads compose a net. Nodes on the net are points of bifurcation and/or points of confluence because the lines are directed. Then errors of closure would be apparent at the confluence points of the surveying lines. This paper deals with the error handling by Ino to make maps. He distributed the revealed error at the confluence point among adjacent points on the newly surveyed line and did not modify existing lines already surveyed.

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This paper examines the transition of cosmology in Fushimi in the 18^th century. In this period, Japan experienced a transition in scientific knowledge from pre-modern astrology to scientific astronomy under the influence of newly imported Western sciences mainly from the Netherlands. Local intellectuals were also the case for this transition. In order to examine this period, we study two observational cases in Fushimi: aurora observation in 1770 and night sky watching with a telescope in 1793. While the record of the former reflects traditional oriental astrological aspects, the latter heavily involves aspects of modern Western science. We examine these records and the cultural context to understand why Fushimi hosted these events, who the networks of local intellectuals were that supported these efforts, and how Japanese intellectuals accepted Western sciences to shift their cosmology away from traditional oriental astrology. These are important case studies as they reveal how Eastern and Western cosmologies overlapped and made a transition while Japan was at a crossroads, not only in terms of trades or travels but also intellectuals and their cosmology.

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The true north and magnetic north are not drawn in the maps of 1:36000 made by INO Tadataka at the beginning of 19th century. In this paper, the author developed method of estimation for the geographic meridian and magnetic meridian for digitized Ino maps. Correlation index between longitudes in the actual digital map of the Geospatial Information Authority of Japan and coordinates in the rotated map image becomes the maximum when the north of rotated map matches to the true north. In this way we were able to fix the north in Ino map of 1:36000.

Ino had believed that the magnetic north was equivalent to true north anywhere through surveying and making maps of Japanese Islands. Therefore, north-south direction in his maps of 1:216000 is magnetic meridian which crosses parallels drawn at right angles. Notwithstanding lack of parallels in the map of 1:36000, we were able to fix the magnetic north comparing with the parallel of the map of 1:216000. This method is the same as true north fixing.

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 At the beginning of the 19^th century, Ino observed the apparent altitudes of stars crossing the meridian to calculate latitude. Then, he revised the values using astronomical refractions provided in Rekisho Kosei Kohen, a Chinese version of a European astronomy book published in 1742. Before starting a field survey, he prepared an inventory of the most recently observed altitudes of stars at his home observatory, which was located at a latitude of 35 degrees 40.5 minutes. During a field survey, he also observed the altitudes of stars at a survey site. The difference in latitudes between the site and his observatory could be obtained from the difference in altitudes of the same star. Using this method, he fixed the latitudes of 1,220 sites on the Japanese Archipelago. It is worth noting that he did not use a catalog of stars, but an inventory of star altitudes he had prepared, although he obtained star declinations for the year, which were derived from declination and precession in the Gisho Kosei catalogue of stars, a Chinese version of a European astronomy book published in 1752.

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　江戸時代後期、天文学を教えながら全国を旅した男がいた。彼の名は朝野北水。彼の資料は全国各地に残されている。その内容は、天文学の初歩的なものであったが、暦の計算や惑星の見え方などを表や図を使って説明した。彼の活動には、現代の天文教育にも通じる要素が多く含まれている。本論文では、出自が明確な資料群に着目し、北水の講義内容を明らかにした。その結果、彼の講演がどのように受け入れられたかを知ることができた。藩校の教師役や商家の人々など、さまざまな立場の人が北水の講義に耳を傾けていることがわかった。

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歴史上の出来事や人物に焦点を当てて,そこに現代のプロジェクトマネジメントの知識体系を重ねると,新鮮な感動と貴重な教訓が得られると考える.今回は,200年以上前の江戸時代に,徒歩を基本ツールとして,55歳から17年間に渡って日本沿海を実測した伊能忠敬について報告する.本報告は,筆者が訪れた千葉県の佐原にある伊能忠敬記念館の資料や写真,その他の文献を参考に,あくまでもプロジェクトマネジメントの視点から考察したものである.

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The first cosmology introduced in China was Aristotelian during the time of Matteo Ricci. However, after the introduction, Chinese cosmology switched to the Tychonic world system because of the practical need for precise astronomical knowledge during the second generation of Jesuit Missionaries. In this article, discussing the characteristics of Chinese cosmology, its realised achievements are also described. The former is the Tychonic system and the latter is the Jianjie zongxing-tu; or the Visiblesky Planisphere. The Chinese efforts over longer range not only to introduce the scientific materials from the West to be used as deemed necessary for the Chinese state and society; but also, the active works undertaken, the instruments manufactured and observations made are also checked so as to understand the characteristic perspective. The later development of astronomical activities, like the calendar reform in the early Qing dynasty is also been investigated; furthermore, the place of these astronomical activities in the scientific perspective promoted by the state is also examined. In this connection the introduction of Kepler's laws is also discussed.

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