Posted: Tue Mar 09, 2010 1:42 am
Hello,
A number of definitions in astronomy (for the benefit of all newbies):
Celestial sphere: an imaginary sphere of the heavens on the surface of which all celestial bodies appear to be located; once thought by the ancients to be an actual, crystalline physical sphere. The daily rising and setting of the stars and planets (diurnal motion) was thought to be the result of the diurnal motion of the celestial sphere.
Zenith: the point on the celestial sphere that is directly overhead (not the same as Midheaven).
Nadir: the point on the celestial sphere that is directly below - directly opposite Zenith (not the same as IC).
Local Meridian: the great vertical circle perpendicular to the horizon that also passes through the North and South points on the horizon as well as Zenith and Nadir.
Ecliptic: The apparent annual path of the Sun around the Earth (actually the plane of the Earth?s orbit around the Sun).
Midheaven, Medium Coeli (MC): the intersection of the local meridian with the ecliptic above the horizon at a particular location. When sun is located on the MC, it is exactly apparent noon (Local apparent time is exactly 12 noon). MC is also the greatest altitude a sun can reach during the day. MC is not the same as Zenith.
Immum Coeli (IC): the intersection of the local meridian with the ecliptic below the horizon at a particular location. When sun is located on the IC, it is exactly apparent midnight (Local apparent time is exactly 12 midnight). IC is also the lowest altitude a sun can reach during the night. IC is not the same as Nadir (though some astrologers seem to think so due to the translation of the words IC which is latin for ?lowest of the sky? and Nadir which the Arabic for similar term).
Culminating: when a body (planet or fixed star) intersects the Local Meridian above the horizon during its diurnal/daily motion. When the sun does this, it is noon - technically this is Local Apparent Noon. Culminating needs not be at the Zenith. When a body culminates, it has the greatest altitude of the day (not necessarily 90 degrees because culminating needs not be at the Zenith!).
Anti-Culminating: when a body (planet or fixed star) intersects the Local Meridian below the horizon during its diurnal/daily motion. When the sun does this, it is midnight - technically this is Local Apparent midnight. Anti-Culminating needs not be at the Nadir. When a body culminates, it has the lowest altitude of the day (not necessarily -90 degrees because anti-culminating needs not be at the Nadir!).
All stars and planets culminate and anti-culminate at some point during the day/night but they do not culminate at the zenith (or anti-culminate at the Nadir). Only stars (or planets) that have declinations equal to the geographical latitude of the place would culminate exactly on the zenith and anti-culminate exactly on the Nadir.
As Sun has the maximum declination of 23d 26m, places with geographical latitudes greater than 23d 26m (North and South) will never see the sun culminates at the zenith (or anti-culminates at the Nadir). Places with geographical latitudes between 23d 26m North and 23d 26m South can see the sun culminates at the Zenith twice a year.
The stars have declinations that do not change much (at least not in a lifetime!). They actually do change at the rate similar to the rate of the precession. So, stars that do not have declinations equal to the geographical latitude of the place will never culminate at the zenith. So, stars that have declinations equal to the geographical latitude of the place will always culminate at the zenith and these stars are called ?stars of the place?. For example, the latitude of London is approximately 51N30. The star Etamin (gamma-Draco) has the declination of about +51d29m. So, Etamin is the star of London (and places that have the same geographical latitude as London). Etamin would culminate at the Zenith in London sometime during the day or night. BTW there is another star that can be considered as the star of the place. It is the star that touches the horizon but does not cross it. This happens for stars whose declinations are the same as (90 ? geographical latitude of the place). For example, the latitude of London is approximately 51N30. 90 ? 51N30 = 48d30m. The star Talitha (iota-Ursa Major) has the declination of approximately 48d. Hence, Talitha can also be the star of London (and other places whose geographical latitudes are the same to London). These stars remain as the stars of the place until about 100 years or so (when the declinations of the stars change due to the precession of the equinox). Then, we will have new stars as stars of the place.
Now back to MarkC question.
Similarly, as long as you are born when a star is rising (at a certain place), then it rises with whatever degree of the ecliptic rising. Mathematically, this is when the Oblique Ascension of the star is the same as the Oblique Ascension of degree of the ecliptic rising.
As an example the time that Spica rises in London according to Solar Fire is 9:14 pm on March 9 2010. So, anybody born at 9:14pm, March 9 2010 in London would have Spica rising. The time, date and place are already fixed, hence, the ASC and MC are also fixed for this person (Asc = 25d10m Libra and MC = 3d28m Leo). You cannot have a different Asc and MC. We would say that when a person is born at 9:14pm, March 9 2010 in London, Spica rises with 25d10m Libra and Spica rises with 3d28m Leo culminating. In fact, Spica would always rise with 25d10m Libra in London (at least for one generation) ? only that it occurs at different times of the day throughout the year (due to its phase with the sun).
A number of definitions in astronomy (for the benefit of all newbies):
Celestial sphere: an imaginary sphere of the heavens on the surface of which all celestial bodies appear to be located; once thought by the ancients to be an actual, crystalline physical sphere. The daily rising and setting of the stars and planets (diurnal motion) was thought to be the result of the diurnal motion of the celestial sphere.
Zenith: the point on the celestial sphere that is directly overhead (not the same as Midheaven).
Nadir: the point on the celestial sphere that is directly below - directly opposite Zenith (not the same as IC).
Local Meridian: the great vertical circle perpendicular to the horizon that also passes through the North and South points on the horizon as well as Zenith and Nadir.
Ecliptic: The apparent annual path of the Sun around the Earth (actually the plane of the Earth?s orbit around the Sun).
Midheaven, Medium Coeli (MC): the intersection of the local meridian with the ecliptic above the horizon at a particular location. When sun is located on the MC, it is exactly apparent noon (Local apparent time is exactly 12 noon). MC is also the greatest altitude a sun can reach during the day. MC is not the same as Zenith.
Immum Coeli (IC): the intersection of the local meridian with the ecliptic below the horizon at a particular location. When sun is located on the IC, it is exactly apparent midnight (Local apparent time is exactly 12 midnight). IC is also the lowest altitude a sun can reach during the night. IC is not the same as Nadir (though some astrologers seem to think so due to the translation of the words IC which is latin for ?lowest of the sky? and Nadir which the Arabic for similar term).
Culminating: when a body (planet or fixed star) intersects the Local Meridian above the horizon during its diurnal/daily motion. When the sun does this, it is noon - technically this is Local Apparent Noon. Culminating needs not be at the Zenith. When a body culminates, it has the greatest altitude of the day (not necessarily 90 degrees because culminating needs not be at the Zenith!).
Anti-Culminating: when a body (planet or fixed star) intersects the Local Meridian below the horizon during its diurnal/daily motion. When the sun does this, it is midnight - technically this is Local Apparent midnight. Anti-Culminating needs not be at the Nadir. When a body culminates, it has the lowest altitude of the day (not necessarily -90 degrees because anti-culminating needs not be at the Nadir!).
All stars and planets culminate and anti-culminate at some point during the day/night but they do not culminate at the zenith (or anti-culminate at the Nadir). Only stars (or planets) that have declinations equal to the geographical latitude of the place would culminate exactly on the zenith and anti-culminate exactly on the Nadir.
As Sun has the maximum declination of 23d 26m, places with geographical latitudes greater than 23d 26m (North and South) will never see the sun culminates at the zenith (or anti-culminates at the Nadir). Places with geographical latitudes between 23d 26m North and 23d 26m South can see the sun culminates at the Zenith twice a year.
The stars have declinations that do not change much (at least not in a lifetime!). They actually do change at the rate similar to the rate of the precession. So, stars that do not have declinations equal to the geographical latitude of the place will never culminate at the zenith. So, stars that have declinations equal to the geographical latitude of the place will always culminate at the zenith and these stars are called ?stars of the place?. For example, the latitude of London is approximately 51N30. The star Etamin (gamma-Draco) has the declination of about +51d29m. So, Etamin is the star of London (and places that have the same geographical latitude as London). Etamin would culminate at the Zenith in London sometime during the day or night. BTW there is another star that can be considered as the star of the place. It is the star that touches the horizon but does not cross it. This happens for stars whose declinations are the same as (90 ? geographical latitude of the place). For example, the latitude of London is approximately 51N30. 90 ? 51N30 = 48d30m. The star Talitha (iota-Ursa Major) has the declination of approximately 48d. Hence, Talitha can also be the star of London (and other places whose geographical latitudes are the same to London). These stars remain as the stars of the place until about 100 years or so (when the declinations of the stars change due to the precession of the equinox). Then, we will have new stars as stars of the place.
Now back to MarkC question.
Solar Fire also gives the times of the rising, culminating, setting and anti-culminating of the stars and planets. As long as you are born when a star is culminating (at a certain place), then it culminates with whatever is the MC. Mathematically, this is when the Right Ascension of the star is the same as the Right Ascension of degree of ecliptic culminating (aka RAMC ? Right Ascension of MC).How can you trace stars co-arising with the Midheaven using such software? Doesn't the culminating position of stars listed in this way reflect the local horizon Zenith rather than the Midheaven aligned to the ecliptic?
Similarly, as long as you are born when a star is rising (at a certain place), then it rises with whatever degree of the ecliptic rising. Mathematically, this is when the Oblique Ascension of the star is the same as the Oblique Ascension of degree of the ecliptic rising.
As an example the time that Spica rises in London according to Solar Fire is 9:14 pm on March 9 2010. So, anybody born at 9:14pm, March 9 2010 in London would have Spica rising. The time, date and place are already fixed, hence, the ASC and MC are also fixed for this person (Asc = 25d10m Libra and MC = 3d28m Leo). You cannot have a different Asc and MC. We would say that when a person is born at 9:14pm, March 9 2010 in London, Spica rises with 25d10m Libra and Spica rises with 3d28m Leo culminating. In fact, Spica would always rise with 25d10m Libra in London (at least for one generation) ? only that it occurs at different times of the day throughout the year (due to its phase with the sun).