Methanespirit
August 22nd, 2001, 08:49 PM
RA is also used to determine where the Earth is in its orbit around the Sun. Since we are viewing the Sun from the Earth, it is the Sun that appears to travel the Zodiacal circle. (This path of the annual solar motion is called the "ecliptic".) The Sun appears to make one lap of the Zodiac in 365.2564 Earth days. Because the Earth's orbit is slightly elliptical the Sun appears to travel faster during the winter months than in the summer. This can be verified by noting the daily motion differences in your ephemeris in July compared with those of January. This is due to the Earth being closer to the Sun in the winter months (northern hemisphere) than in the summer. Where the appearent Sun (that which is visible) is in its orbit, around the Zodiac, is called the RA of the appearent Sun, or it is simply called R.A. This value is given daily in the more complete ephemerides. But for Astrological purposes, RA is used to find where the Mean Sun (MS) is in a FICTITIOUS ORBIT, that is, one where the Sun does not have any annual variance of motion. This is why it is called the Mean Sun, "Mean" meaning average motion. The RA or Sidereal Time listed daily in your ephemeris is also the Mean Sun. The three terms are all the same but used in different contexts.
If you look over your ephemeris in the daily listings you will find that the Sidereal Time (ST) changes a little each day. The average (or mean) change is calculated by 24 hours (of RA ) divided by 365.2564 ,( the amount of days for the Earth to orbit the Sun.) This yields a mean daily incrment of :03:56.546 minutes of RA per day. This change is caused by the Earth's daily movement, measured in RA, around the Sun. Since it is nearly 1/2 second extra in daily increment, the ST will vary in the ephemeris from :03:56 to :03:57 per day. This slight daily RA change is also calculated in every Astrological chart. It is called the RA increment or sometimes just "increment". Its correct value, considering that a chart is most likely calculated during mid-day, sometime, is determined by the Greenwich time multiplied by 9.856 seconds per hour. Then that value is added to the ST of that day which gives the MS for the Astrological chart. Its value should be added for future reference information of the chart. For example let us say we are doing a chart for a person born on May 25, 1967 at 14:00 hours PDST.
PDST of birth...........................................14:00:00 5/25
correction to standard time....................-01:00:00
PST..........................................................13:00:00
diff to UT................................................+08:00:00
UT of birth................................................21:00:00 5/25
incr 9.856" X 21.000 hrs= 207" or..........00:03:27 (add to ST)
ST for 5/25/67.........................................16:07:34
MS/n (natal) ..........................................16:11:01
The foregoing is the correct way to begin calculations to an Astrological chart.
If you look over your ephemeris in the daily listings you will find that the Sidereal Time (ST) changes a little each day. The average (or mean) change is calculated by 24 hours (of RA ) divided by 365.2564 ,( the amount of days for the Earth to orbit the Sun.) This yields a mean daily incrment of :03:56.546 minutes of RA per day. This change is caused by the Earth's daily movement, measured in RA, around the Sun. Since it is nearly 1/2 second extra in daily increment, the ST will vary in the ephemeris from :03:56 to :03:57 per day. This slight daily RA change is also calculated in every Astrological chart. It is called the RA increment or sometimes just "increment". Its correct value, considering that a chart is most likely calculated during mid-day, sometime, is determined by the Greenwich time multiplied by 9.856 seconds per hour. Then that value is added to the ST of that day which gives the MS for the Astrological chart. Its value should be added for future reference information of the chart. For example let us say we are doing a chart for a person born on May 25, 1967 at 14:00 hours PDST.
PDST of birth...........................................14:00:00 5/25
correction to standard time....................-01:00:00
PST..........................................................13:00:00
diff to UT................................................+08:00:00
UT of birth................................................21:00:00 5/25
incr 9.856" X 21.000 hrs= 207" or..........00:03:27 (add to ST)
ST for 5/25/67.........................................16:07:34
MS/n (natal) ..........................................16:11:01
The foregoing is the correct way to begin calculations to an Astrological chart.