A Chinese Innovation Based on Western Methods: The Double-Epicycle Solar Model in the Lixiang kaocheng, 1722

2019 ◽  
Vol 50 (2) ◽  
pp. 174-191
Author(s):  
Guangchao Wang ◽  
Xiaochun Sun
Keyword(s):  
Observational Data ◽  
Solar Model ◽  
Solar Motion ◽  
Mathematical Astronomy

This article attempts to show how an effort was made by Chinese astronomers to improve on the solar model under the auspice of Emperor Kangxi, in circumstances of the merging of Western and Chinese mathematical astronomy. The result of this effort is the Lixiang kaocheng. Different from the eccentric solar model in the previous calendars, Lixiang kaocheng invented a double-epicycle model to describe the solar motion, aiming at bringing computations into agreement with observation. The observational data used for determining the parameters of solar model might be obtained with Tychonic instruments. But it is also possible that these “observational data” might have been derived from Western astronomical tables. Although actual observations did become more accurate, it did not reflect upon the revision of the solar model. The accuracy of the solar model in the Lixiang kaocheng did not increase very much compared with the previous models.

scholarly journals New Moon's Visibility and International Islamic Calendar for the American Region 1407H - 1421H

1995 ◽  
Vol 12 (2) ◽  
pp. 279-284
Author(s):  
Khalid Shaukat
Keyword(s):  
Nineteenth Century ◽  
Observational Data ◽  
Brightness Contrast ◽  
Tabular Form ◽  
Mathematical Astronomy ◽  
New Moon ◽  
Friendly Competition ◽  
Late Part ◽  
American Region

The International Islamic Calendar Programme relies on calculationsof the new moon's expected visibility. The term "new moon's visibility"gives a wrong connotation, because the astronomical term "new moon"refers to a moon that is completely dark and invisible. Therefore, fromhere on the term "crescent moon" or simply "crescent" will be used for amoon that could be visible after the new moon phase.The problem of predicting the crescent moon's visibility has been ofinterest to astronomers in general for a friendly competition of sightinga young crescent moon and to Muslims for their needs associated withthe Islamic calendar. The earliest astronomical criterion for visibilityappeared in the Babylonian era: the moon's age after conjunction mustbe more than 24 hours, an arc of separation as must be more than 12° orthe moon sets 48 minutes after sunset. Hindus (500-700 C.E.) developeda more elaborate system of calculations with the same as >= 12° criterion.In the eighth to tenth centuries C.E., Muslim astronomers, notablyYa'qub ibn Tariq, Habash, al Khwarizmi, al Farghani, and al Battaniexcelled in mathematical astronomy and developed rules for predictingthe crescent's visibility based on the importance of the crescent's width.A century later, al Biruni recommended al Battani's procedures. In thefifth century, al Sufi and al Kashani still quoted the early Babylonian criterionof as >=12° .In the late part of the nineteenth century, Schmidt recorded observationsin Athens, Greece, throughout a period of twenty years. Fotheringham(1910) and Maunder (1911), who used Schmidt's data and thenadded some more observational data, made the first significant developmentsin criterion for visibility since the time of al Battani. Bruin (1977)developed an independent physics-based criterion involving such variablesas the sky's brightness, contrast, the crescent's intensity, and so on.However, his criterion was only theoretical and its validity needed to beproven by actual observations. Ilyas (1981) modified Bruin's criterion inorder to remove the discrepancy in his method and the actual observationalcriterion of Maunder. All of these suggested criteria for calculatingexpected visibility have been summarized in a tabular form on page15 ...

Current status of special planetary and lunar theories and ephemerides

1966 ◽  
Vol 25 ◽  
pp. 266-267
Author(s):  
R. L. Duncombe
Keyword(s):  
Observational Data ◽  
Current Status ◽  
Numerical Errors

An examination of some specialized lunar and planetary ephemerides has revealed inconsistencies in the adopted planetary masses, the presence of non-gravitational terms, and some outright numerical errors. They should be considered of temporary usefulness only, subject to subsequent amendment as required for the interpretation of observational data.

July 11, 1991 Eclipse Corona Photometry by the Results of Electropolarimetric and CCD-Matrix Observations

1994 ◽  
Vol 144 ◽  
pp. 567-569
Author(s):  
V. Kulidzanishvili ◽  
D. Georgobiani
Keyword(s):  
Solar Corona ◽  
Observational Data ◽  
Solar Limb ◽  
Ccd Matrix

AbstractThe observational data of July 11, 1991 eclipse solar corona obtained by both electropolarimeter (EP) and CCD-matrix were processed. Using these data, the solar corona photometry was carried out. The results of EP data are compared with the ones of CCD data. It must be noted here that the CCD data give us only characteristics of the inner corona, while the EP data show the features of both the inner and middle corona up to 4R⊙. Standard flattening indexϵis evaluated from both data. The dependence of the flattening index on the distance from the solar limb is investigated. The isophotes in Na and Ca lines are plotted. Based on these data some ideas and conclusions on the type of the solar corona are presented.

On The Radii of Ap Stars

1976 ◽  
Vol 32 ◽  
pp. 49-55 ◽  
Author(s):  
F.A. Catalano ◽  
G. Strazzulla
Keyword(s):  
Observational Data ◽  
Line Width ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Ap Stars

SummaryFrom the analysis of the observational data of about 100 Ap stars, the radii have been computed under the assumption that Ap are main sequence stars. Radii range from 1.4 to 4.9 solar units. These values are all compatible with the Deutsch's period versus line-width relation.

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