The days of heliacal setting and rising of a star
Introduction to this software
Our sky is filled with thousands of stars visible with the naked eye. Some of them remain visible all year long. These are the stars which define the geometrical outlines of the northern circumpolar constellations like Ursae Minoris (the Small Dipper), Ursae Majoris (the Big Dipper), Draco, ... On the contrary, the southern circumpolar stars remain invisible to the european, the russian or the north-american observer. This is due to his (her) geocentric latitude. An australian or a south-american observer effectively enjoys a reversed situation : he (she) can see the Triangulum Australe and the Octans but not the Big Dipper nor the Draco, indeed.
In the one and the other cases, most of the stars visible with the naked eye however fill an intermediate area, located between the northern and southern circumpolar areas, which the Sun yearly seems to travel. During its apparent yearly course, the Sun goes near then moves away from everyone of these stars. On their conjunction day, most of them are unseen with the naked eye. Several days, weeks, even months later, they make their heliacal rising, that is to say, their reappearance at dawn. Their heliacal rising puts an end to their yearly period of invisibility which began on their day of heliacal setting, that is to say, on the day they became unseen in the twilight sky.
At intermediate latitudes, most of the stars lie within the northern and southern circumpolar areas. Their daily and yearly periods of invisibility seem all the longer to the northern hemisphere's observer since the star lies far away from the northern circumpolar area.
The yearly period of invisibility of a star - that is to say, the time elapsed between its days of heliacal setting and rising - mainly depends upon its apparent magnitude, its distance from the ecliptic line, the latitude and the altitude of the site chosen for observation, meteorological factors and the visual acuity of the observer. It is necessarily between 0 and 365 days. A star whose yearly period of invisibility is equal to 0 or 365 days is a circumpolar star ; it makes no heliacal setting nor any heliacal rising. Any other star sets and rises heliacally during the year.
Within the form leading to determine the days of heliacal setting and rising of any of the 5041 stars visible with the naked eye mentioned within the Hipparcos catalogue, simply enter the year, the latitude and the altitude of the site chosen for observation, as well as the visual acuity of the observer. The software, which combines the most recent algorithms of astrometry and photometry, will then determine the days of heliacal setting and rising of the star considered, the time elapsed since the setting of the Sun or before the rising of the Sun on the day considered, the heights of the Sun and the star at the time considered, the atmospherical extinction and the brightness of the sky where the star is. A second form will enable you to enter the values of the temperature and humidity rate of the ambient air at the time of heliacal setting or rising of the star, in order to sharpen the results.
Within the form leading to determine the days of heliacal setting and rising of any of the 5041 stars visible with the naked eye mentioned within the Hipparcos catalogue, simply enter the year, the latitude and the altitude of the site chosen for observation, as well as the visual acuity of the observer. The software, which combines the most recent algorithms of astrometry and photometry, will then determine the days of heliacal setting and rising of the star considered, the time elapsed since the setting of the Sun or before the rising of the Sun on the day considered, the heights of the Sun and the star at the time considered, the atmospherical extinction and the brightness of the sky where the star is. A second form will enable you to enter the values of the temperature and humidity rate of the ambient air at the time of heliacal setting or rising of the star, in order to sharpen the results.
About this software : This software leads to determine the dates of heliacal setting and rising of any star visible with the naked eye of the Hipparcos catalog (i.e., 5043 stars) any year between -4712 and 2017. Dates of first publication and successive updates of this software : november 2002 / november 2003 / september 2006 / july 2010
Exclusively at Culture Diff' : Free tests of this sofware are available. Use them to determine the days of heliacal setting and rising of the star of Sirius in 2012 AD, to study the records of the heliacal rising of Sirius in the past of Egypt, next discover its numerous functionalities and possible use.
Author of this software : Karine Gadré, Ph.D. in Astronomy of the University of Toulouse, France, Founder and Header of the Culture Diff' company, Member of the association Les Ankhou which aims at producing and sharing scientific and cultural knowledge.
Software + : This software was conceived within the context of the doctoral dissertation I prepared at the Laboratoire d'Astrophysique de Toulouse-Tarbes, Toulouse, France, on the basis of the most recent developments into Astrometry and Photometry. It led to determine the medium value of the visual acuity of the ancient Egyptian astronomers and to identify every one of the old Egyptian decans to stars visible with the naked eye of the Hipparcos catalog.
Access to the user interfaceThe price of this original astronomy software is 15 euros. This amount includes an unlimited access to the user interface and a free access to any future updates. To purchase this software by credit card or PayPal balance on the PayPal secure payment server, add it to your PayPal Cart. To do so, please click on the following logo :
Further Culture Diff' resources
Dossiers > AstroEgypto : The Egyptian decans : mythical stars
Dossiers > AstroEgypto : The heliacal rising of Sirius in ancient Egypt : a source of historical dating
Dossiers > AstroEgypto : The sky of ancient Egypt : stellar clocks, water clocks and astronomical ceilings
Dossiers > HistoSciences : Astronomie antique et moderne : d'observations en modélisations toujours plus poussées
Publications > Wiki AstroEgypto : Détermination de l'acuité visuelle des astronomes égyptiens
Publications > Wiki AstroEgypto : Astronomical dating proposals of the ancient Egyptian stellar clocks
Publications > Wiki AstroEgypto : Introduction aux méthodes de l'archéoastronomie. Première Partie : Application à l'identification des décans égyptiens
YooKan > Web Interfaces : Applying, to the records of the heliacal rising of Sirius in the past of Egypt, of the software leading to determine the setting and rising days of any star.
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