Ken Ward's Astrology Pages

Astrology Required Accuracy in the Birth Data.

The accuracy of the astrological interpretation is dependent on the birth data, which includes the birth time, longitude and latitude. Errors in these values affect the elements of the interpretation to different degrees.

Birth Time
Longitude
Miles
Latitude

Birth Time

The effects of errors in the birth time and place on the interpretation varies depending on the planetary objects being considered. The effect is most pronounced on the position of the fastest moving elements. The houses are the fastest moving elements.

The ascendent and the houses are most sensitive to the birth time. An error of 4 minutes in the birth time means an error of one degree in the houses.

The moon is next in sensitivity to the birth time. An error of one hour and 49 minutes produces an error of one degree in the moon's position.

After the moon, the position of mercury has a one degree error after about 6 hours.

The sun apparently moves around the earth in about a year. This is about a degree every day through the signs. In one hour, the sun moves about 2½ minutes of arc through the signs. An error of 1 hour in the time for the birth, will mean an error of 2½ minutes of arc in the sun sign.

The position of Mars is one degree in error after about 2 days.

After Mars, the other planets move so slowly that it takes a large error (from about 12 days to 250 days) to make a difference of one degree.

			Degrees of arc
Planet	One revolution (Years)	One revolution (Days)	Daily Motion	Hourly Motion (degrees)	Hourly Motion (degrees and minutes)	Time for 1 degree (Hours)	Time for 1 degree (hours and minutes)
Ascendent	0.003	1.0	360.00	15.00	15 deg 0.00 min	0.07	0 hr 4 min
Moon	0.075	27.3	13.19	0.55	0 deg 32.97 min	1.82	1 hr 49 min
Mercury	0.241	88.0	4.09	0.17	0 deg 10.23 min	5.87	5 hr 52 min
Venus	0.616	225.0	1.60	0.07	0 deg 4.00 min	15.00	15 hr 0 min
Sun	1.000	365.0	0.99	0.04	0 deg 2.47 min	24.33	24 hr 20 min
Mars	1.882	687.0	0.52	0.02	0 deg 1.31 min	45.80	45 hr 48 min
Jupiter	12.000	4380.0	0.08	0.00	0 deg 0.21 min	292.00	292 hr 0 min
North Node	18.000	6570.0	0.05	0.00	0 deg 0.14 min	438.00	438 hr 0 min
Saturn	29.000	10585.0	0.03	0.00	0 deg 0.09 min	705.67	705 hr 40 min
Uranus	84.000	30660.0	0.01	0.00	0 deg 0.03 min	2044.00	2044 hr 0 min
Neptune	165.000	60225.0	0.01	0.00	0 deg 0.01 min	4015.00	4015 hr 0 min
Pluto	248.000	90520.0	0.00	0.00	0 deg 0.01 min	6034.67	6034 hr 40 min

Longitude

An error of fifteen degrees in the longitude makes a difference of one hour in the birth time. An error of one degree in longitude produces an error of 4 minutes in the birth time. This will affect the ascendent and the cusps most, producing an error of one degree in them. An error of 23 degrees in the longitude would produce an error of one degree in the moon's position. The other planetary objects, would be affected considerably less.

Miles

The distance between time zones is about 1000 miles. That is, 15 degrees of longitude represent 1000 miles. One degree is therefore about 1000 /15 miles or 67 miles. An error of 67 miles would therefore produce an error of 4 minutes on the birth time. This would introduce an error of one degree in the ascendent. Of course, the difference in miles between time zones varies. It is about 1000 miles at the equator and zero at the poles.

Latitude

Errors in latitude do not affect the MC and the planetary positions. They affect the ascendent and the house cusps. An error of about 1 degree in latitude produces an error of about half of one degree in the ascendent. One degree of latitude is about 67 miles.