546794_10151261998234855_559549852_n[The first part of this article was first published in 2003 as a page in a previous incarnation of The Classical Astrologer. The present article contains some very minor refinements and an  Addendum, intended as a brief expansion on the significance of the annual event.]

Sirius is a first magnitude star (HR 2491 HD 48915 Flamsteed Number: 9 Bayer Letter: Alpha) in the constellation of Canis Major, with a visual magnitude of -1.46. Sirius is also known as Canicula; the Dog Star and Aschere. Sirius is 2.01 times the size of the Sun and the brightest star in our heavens.

The heliacal rising of the dog star signalled the most searing heat of the Summer, hence the term ‘dog days.’. The star is most easily found by tracing the belt of Orion downwards. Sirius is a binary star with a white dwarf companion, Sirius B. This “pup” is an eight-magnitude star, separated from Sirius by a couple of arcseconds. This makes it exceedingly difficult to see in a telescope because of the great brilliance of Sirius.

Manilus writes of Sirius (the Dog) as one who

“will fashion unbridled spirits and impetuous hearts; it will bestow on its sons billows of anger, and draw upon them the hatred and fear of the whole populace. (The impetuosity of the speaker causes him to utter words before he has time to adapt them to grammar or logic).

Their hearts start throbbing at the slightest cause, and when speech comes their tongues rave and bark, and constant gnashing imparts the sound of teeth to their utterance.orion_sirius_2

Their failings are intensified by alcohol, which gives them strength and fans their savage wrath to flame. No fear have they of woods or mountains, or monstrous lions, the tusks of the foaming boar, or the weapons which nature has given wild beasts; they vent their burning fury upon all legitimate prey.

Lest you wonder at these tendencies under such a constellation, you see how even the constellation itself hunts among the stars, for in its course it seeks to catch the Hare in front.”

( Liber V Astronomica, lines 206-233). See original Latin text.

Sirius has always been considered a very important star, and it was watched diligently. It is also one of the primary stars of navigation. The importance of calculating the heliacal rising and setting of Sirius was recognized in Ancient times and is still relevant today. The table below shows the anticipated times of the heliacal rise and set dates in three locations over a span of 2800 years.

The Original Table in Italian is @

As is true of any star, Sirius is only visible between the time of its helical rising and setting. Conversely, it is invisible from the time of heliacal setting until its heliacal rising.

The “heliacal rising” is the first day when the star rises and the Sun is far enough below the eastern horizon to make it visible in the morning twilight. In the same way, the “heliacal setting” is the last day when the star sets and the Sun is far enough below the western horizon to make the star visible in the evening twilight. This is not to be confused with what is called “cosmic rising”. In the latter case, it is not possible to see the star, due to the light of the Sun.

Because the magnitude and brilliance of stars differ considerably, their heliacal risings and settings occur with different altitudes of the Sun below the horizon (this is called in Latin “arcus visionis” of the star).

For example, the Sun’s altitude which makes Sirius visible (-7°) is quite smaller than the altitude (-11°) that allows Antares to be visible in the early dawn or twilight sky. This is because Sirius is brighter than Antares and can, therefore, be seen in a lighter sky. The approximation in calculations of these heliacal rising and setting times over the centuries is unavoidable .(see J. Meeus, Mathematical Astronomy Morsels, Richmond, Virginia 1997, pp. 289-2960.)

However, this table serves as a very close approximation of the periods of the first and last dates of the visibility of Sirius in relation to the horizon. It is oriented from the horizon (height 0°), with the Suns place to a negative height of 7°.

It may be difficult for many contemporary astrologers to understand the phenomena of first and last visibility of a celestial body. This is due to the unfortunate modern divorce of astrology from her sister science, astronomy.

Sky Map 1

In ancient and Classical astrology, no such divorce had occurred and the heavens were watched very closely. The sky maps below are designed to help illustrate the concept of heliacal rising more clearly.

Sky Map 1 was generated using SkyChart software, set for sunrise in Rome, 08 August 2000. 6:19 am. The red line is the local horizon. The Sun is seen at the far left. Sirius is the bright star in the constellation Canis Major. Note that the Sun is on the eastern horizon, but Sirius is still not visible in the morning twilight.

Sky Map 2

Sky Map 2 is for the same date and location, at 05:38:01 am, which is the precise time of the rising of Sirius. Sirius is seen ascending on the eastern horizon but is still not visible due to the morning twilight.

Sky Map 3 is set for one day after the anticipated date of the heliacal rising of Sirius in Rome according to the table, on 12 August 2000 at 3h34m UT — 4:31am LMT.

Star Map 3
Star Map 3

This is the precise time of the heliacal rising of Sirius, seen rising on the eastern horizon. The star is visible because it has cleared the necessary -7 negative height of the Sun, for the first time after approximately 3 months of invisibility This is the true heliacal rising of Sirius for the date given. On the anticipated date of 11 August, the Sun’s altitude is only -6°52’, and we cannot be sure of the visibility of Sirius.

This article above was written whilst in conversation with Giuseppe Bezza. I’m indebted to his assistance and guidance during the Summer of 2003. I heartily recommend reading his page “Alcuni testi sulla levata eliaca di Sirio” at Cielo e Terra. The compendium he offers in translation is an indispensable contribution to the study of ancient star lore in general and to Sirius in particular.


Addendum 16 August 2020

In the Roman Empire, the Lychnapsia was a festival of lamps or “lights” held on August 12 and was held in honour of Isis. The festival originated in Egypt. (See Salem, “The Lychnapsia Philocaliana“, p. 165.) The dates of the celebration vary as does the precessed event, but was observed for several days before and after the astronomical occurrence.

From an astronomical or astrotheological point of view, The Lights of Isis is a term given to the observations and celebrations connect to the apparent rising of Sirius which coincided with the inundation of the Nile, thus assuring fertility and abundant, healthy crops. However, the star was also examined for its potential by considering the many attributes listed by Giuseppe Bezza. It was not a matter taken for granted. Some considerations might auger for a poor or scant harvest, for example.

The annual occurrence of this sighting also had deep significance beyond the physical  Sirius is Isis and the constellation Orion is Osirus. The term “dog days of Summer is in reference to the period of intense heat associated with the moment of the apparent rising of Sirius. She had to be visible and not outshone by the Sun.

This phenomenon also describes the process by which Isis acts to ‘raise up’ Osirus. The constellation of Osirus is today refered to as Orion and this part of the heavens was of particular importance to many cultures. It has been shown how the three pyramids of Giza are arranged to reflect the stars in Orion’s belt, consisting of the three bright stars Alnitak, Alnilam and Mintaka. These stars are also known as the Three Kings.

“The central star in Orion’s belt is named “Alnilam”, which means ‘string of pearls’.  Ancient Egyptians believed Alnilam portended fleeting public honours to those born under its influence, but we may also find here the source for references to the “pearly gates” that the dead pass through from this life into the next. It was as though the dead travelled into the afterlife through the region of the Orion constellation, where they met the god of the dead, Osiris, and passed through the string of pearls at the centre of his belt. One of the few specific references to known constellations that occurs in the Bible appears in the Old Testament Book of Job, in which God admonishes Job with the question: “Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion?” Job is being asked whether he has the power loose the bands of death.” ( Orion and the pearly gates.) 

The roots of virtually every society that ever existed held the reading of stars as of the utmost and most natural element of all. We find this in Egypt, and not only in major religious traditions such as Judaism, Hinduism, and Islam but in what has been passed down to us from the painters of the Caves of Lascaux, the Druids and Vedic sages. We are made of stardust and the inextricable understanding of the relationship between the microcosm and macrocosm is ubiquitous.

These universal observations have been ‘personalized’ from one culture to another, so we have the Milky Way referred to by Hindus as the Celestial (or true) Ganges and by the Egyptians as the Celestial Nile. The Hermetic dictum “as above, so below” is how we understood our state of being and place in the cosmos until very recently.

This ‘great divorce’ is a form of spiritual alienation that negatively affects how we treat the natural world, as we block out the sight of the stars with artificial light. Thankfully, this is beginning to change and we now see through the lies of a universe devoid of divinity and hence humanity devoid of any sense of connection to the vast web of creation.

Osiris on His back (note the position of the three belt stars) with Isis-Sopdet below (framed by the trees), upraising Him. See httpsisiopolis.com20140727isis-sirius-rising#~text=OsirisonHisback(notetheposi


© 2003, 2012, 2020

3 thoughts on “SIRIUS – HELIACAL RISING & SETTING – 800 BC – 2000 AD

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