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- Gislén, Anna, et al.
(författare)
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On the optical theory of underwater vision in humans
- 2004
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Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 21:11, s. 2061-2064
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Tidskriftsartikel (refereegranskat)abstract
- Defocus changes the visual contrast sensitivity function, thereby creating a complex curve with local dips and peaks. Since underwater vision in humans is severely defocused, we used optical theory and the phenomenon of spurious resolution to predict how well humans can see in this environment. The values obtained correspond well with experimental measurements of underwater human acuity from earlier studies and even point to an opportunity for humans with exceptional contrast sensitivity to see better underwater than the children in those studies. The same theory could be useful when discussing the visual acuity of amphibious animals, as they may use pupil constriction as a means of improving underwater vision.
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| 2. |
- Eade, Chris J., et al.
(författare)
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“The Whole Moon was Eaten”: Southeast Asian Eclipse Calculation
- 1998
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Ingår i: Journal of Southeast Asian Studies. - 0022-4634. ; 29:2, s. 309-318
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Tidskriftsartikel (refereegranskat)abstract
- One might classify earthquakes and volcanic eruptions as “natural disasters”, whereas comets and eclipses might be described merely as “natural curiosities”. In earlier times, however, all were equally frightening, signs that the gods were angry.A form of protection against eclipses was available, however, in the sense that prediction provided a means of countering the event. Consequently one main function of the astronomer/astrologer (henceforth “hora”) in his society was to warn his patron that the sky would darken and the birds stop singing at such and such a time on such and such a day.
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| 4. |
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| 5. |
- Gislén, Lars
(författare)
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A Hypothetical Romakasiddhānta Calendar
- 2019
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Ingår i: Journal of Astronomical History and Heritage. - 1440-2807. ; 22:2, s. 339-341
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Tidskriftsartikel (refereegranskat)abstract
- The Romakasiddhānta is a quite special Hindu luni-solar canon being the only one using Metonic intercalation and implementing a tropical solar year. As the name suggests it has a Hellenistic origin. The known facts about the canon are scanty but in spite of this it is possible to draw some conclusions from them. A hypothetical calendar based on its known characteristics is investigated below
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| 6. |
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| 7. |
- Gislén, Lars
(författare)
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An analysis of the golden numbers on the calendar disk of the astronomical clock in Lund
- 2021
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Ingår i: Journal of Astronomical History and Heritage. - 1440-2807. ; 24:1, s. 77-82
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the golden numbers on the calendar disk of the astronomical clock in Lund, Sweden. Using methods of internal consistency we find printing errors and locate several golden numbers misplaced by one day. However, from the available data it is not possible to determine the principles that were used for calculation of the location of these golden numbers when the calendar disk was restored in 1923.
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| 10. |
- Gislén, Lars, et al.
(författare)
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Analysis of the New Moon Times on the Disk of the Astronomical Clock in Gdansk, Poland.
- 2022
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Ingår i: Journal of Astronomical History and Heritage. - 1440-2807. ; 25:1, s. 75-82
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Tidskriftsartikel (refereegranskat)abstract
- The calendar disk of the fifteenth century astronomical clock in the church of Saint Mary in Gdansk (Poland) contains a wealth of astronomical and calendrical data. We make a statistical analysis of the mean conjunction times of all the mean New Moons as represented on the disk for four Metonic 19-year cycles. We find that the conjunction times were generated using the Alfonsine value for the length of the synodic month and with a mean longitude correction from the Alfonsine meridian (Toledo in Spain) by 1 hour and 16 minutes. This indicates a location with a longitude of a little more than 19° east of Toledo but due to the uncertainty of the actual locations in longitude at the time it is not possible to point out a specific location. The method of calculating the conjunction times differs from other contemporary calendars and has considerably less quality than other contemporary conjunction lists.
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