Most astrologers concern themselves only with the positions of the Sun, Moon and planets as seen from a topocentric or a geocentric perspective. Other phenomena, such as fixed stars and comets, when considered at all, are generally misused.
I. Fixed Stars
A. Since each of the stars has the nature of one of the planets the modern astrologer treats them as such. Observing the celestial longitude of the star, he presumes it is on the ecliptic and proceeds to apply aspects and interpretations in the usual manner. Aspects by the planets to the angles of a chart, and hence to fixed stars at those angles, are valid regardless of the latitude of the star, because the "angle" is not just a point on the geographical horizon, but also a great circle on the celestial sphere. Nevertheless, most of the fixed stars are not on the ecliptic, but they have variant celestial latitudes. As long as both bodies are close to the ecliptic there will be no significant error, but if one of them has appreciable celestial latitude the error in aspect can be quite large.
By and large, for the main aspects (conjunction, opposition, sextile and trine) a distance of 60 degrees in celestial latitude between the two bodies may result in an error of about 50 degrees in longitude. In this case, the planetary aspects should not be applicable to the fixed stars.
In ancient times, the stars that were rising, setting, and culminating at the time of birth (the stars one was really born under) were considered to be of primary importance. Each of them was given the nature of one or more of the planets and from them the astrologer could delineate much of what may befall the native. For example:
• Canopus (Alpha (α) Carina in Argo Navis)
Rising: it was supposed to give a love of travel and also to instigate fights and quarrels resulting in lawsuits; the native however could channel these tendencies constructively, with astuteness and a sense of real earnestness. [Fixed Stars and Their Interpretation, Elsbeth Ebertin, 1928]
Culminating: it was signifying great glory, fame and wealth, dignity and authority by the help of an old clergyman or influential person.
• Rigel (Beta (β) Orion)
Rising: was considered to bestow good fortune, preferment, riches, great and lasting honors.
Culminating: military or ecclesiastical preferment, anger, vexation, magnanimity, much gain acquired by labor and mental anxiety, lasting honors.
• Pollux (Beta (β) Gemini)
Rising: Bad eyes, blindness, injuries to the face, sickness, wounds, imprisonment, ephemeral honor and preferment.
Culminating: Honor and preferment but danger of disgrace and ruin.
[Fixed Stars and Constellations in Astrology, Vivian E. Robson, 1923]
B. Another error committed by modern astrologers, is the complete neglect of the star's apparent magnitude. Traditionally, bright stars were considered much more important in a chart than were the dimmer ones and ancient astrologers made much of the changing magnitude of the planets, giving them much more importance as they became brighter. And variable stars such as Mira, which at times cannot even be seen with a small telescope, could only be delineated by carefully noting their periods.
1. What remained after billions of years of planetary encounters was an extraordinarily large cloud of comets extending outward from orbits beyond Pluto in all directions. A virtual spherically shaped cloud of comets (named Oort) surrounds the Sun at a distance from 1,000 to 100,000 astronomical units. There is also a disk shaped source of comets that extends from 35-40 AU out from the Sun to about 1,000 AU. This disk-shaped Kuiper Belt blends with the spherical Oort Cloud at about 1,000 AU. Since the Oort Cloud is spherical, long-period comets can appear to approach the Sun from any point in space. Short-period comets, originating from the Kuiper Belt, always appear to emanate from a band along the ecliptic plane (the plane that contains the planetary orbits). They are temporary visitors and periodic comets, such as Halley's, are always around. It is just that they are too far away to be seen most of the time. A comet is a valid astrological entity only if it can be seen with the naked eye. And the brighter the apparition the more important it becomes astrologically.
When a comet appears in the sky, its celestial latitude can be quite large. As it approaches perihelion, it begins to get very close to the ecliptic. When the comet appears, even at the higher latitudes, it activates the constellation its head is in. When it gets to within ten or fifteen degrees of the ecliptic it is said to be in the zodiac. When the comet is first visible to the naked eye (magnitude about +5) it is said to have entered the solar system. The comet will generally enter the solar system before it arrives in the zodiac. Therein the normal planetary aspects apply.
2. Comets are comparatively rare astrological events. Less than 2% of those born since 1900 have a comet in their birth chart. However, every visible comet that enters our solar system will energize our natal planets as transits.
3. Using progressions, a year of future time is assumed to be accounted for by a day's movement of the planets. But comets move much faster than do planets. A day's movement of a comet is equivalent to 30 days, sometimes as little as a week, of future time as measured from the instant it enters the zodiac. Nevertheless, when it enters our solar system its orbit will be perturbed by the planets, especially by Jupiter. These perturbations are not entirely predictable. As a result, the comet's location and brightness may vary from that given in early accounts, such as in ephemerides published several months ago. The astrology of events such as comets requires visual observation if at all possible.
I am not sure whether all computerized astrological calculations provide for the above mentioned specifications. However, in the case of handmade charts, both the celestial latitude and the apparent magnitude of stars and comets should be taken into account.