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Dating historical Arabic observations


Thomann, Johannes; Gautschy, Rita (2020). Dating historical Arabic observations. Proceedings of the International Astronomical Union, 14(A30):163-166.

Abstract

The first visibility of the lunar crescent signals the start of a new month in the Islamic calendar. The eminent astronomer Ḥabash al-Ḥāsib sib developed a method of uncompromising complexity for predicting the visibility of the lunar crescent. He derived his threshold value from a moonwatch carried out at different places in Iraq on November 17th, 860 CE. We will allude to a few modern visibility criteria as well and highlight the uncertainties of today’s calculations when converting historical Arabic into Julian or Gregorian dates. Tables of first visibility of the lunar crescent for different locations are provided for the purpose of date conversions. Since the Islamic calendar was based on the observation of the lunar crescent, historical dates imply information on positive and negative sightings of the lunar crescent. From such information estimations of cloudiness in different regions of the Islamic world can be extracted.

Abstract

The first visibility of the lunar crescent signals the start of a new month in the Islamic calendar. The eminent astronomer Ḥabash al-Ḥāsib sib developed a method of uncompromising complexity for predicting the visibility of the lunar crescent. He derived his threshold value from a moonwatch carried out at different places in Iraq on November 17th, 860 CE. We will allude to a few modern visibility criteria as well and highlight the uncertainties of today’s calculations when converting historical Arabic into Julian or Gregorian dates. Tables of first visibility of the lunar crescent for different locations are provided for the purpose of date conversions. Since the Islamic calendar was based on the observation of the lunar crescent, historical dates imply information on positive and negative sightings of the lunar crescent. From such information estimations of cloudiness in different regions of the Islamic world can be extracted.

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Additional indexing

Item Type:Journal Article, not_refereed, original work
Communities & Collections:06 Faculty of Arts > Institute of Asian and Oriental Studies
Dewey Decimal Classification:180 Ancient, medieval & eastern philosophy
290 Other religions
Scopus Subject Areas:Health Sciences > Medicine (miscellaneous)
Physical Sciences > Astronomy and Astrophysics
Health Sciences > Nutrition and Dietetics
Health Sciences > Public Health, Environmental and Occupational Health
Physical Sciences > Space and Planetary Science
Language:English
Date:2020
Deposited On:10 Mar 2020 15:18
Last Modified:29 Jul 2020 14:48
Publisher:Cambridge University Press
ISSN:1743-9213
OA Status:Closed
Publisher DOI:https://doi.org/10.1017/S1743921319003983

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