posted December 12, 2003 01:47 PM
From http://www.karmastrology.com/ast_scht.shtml :SOLAR CHART
The phrase, solar chart, is astrological shorthand for a natal astrological chart for which no time of birth is available.
Mathematically speaking the solar chart is quite simple. It is commonly done in one of two ways, both of which give similar results.
The positions of the natal planets are calculated either for sunrise on the date of birth, or the planets are calculated for 12 Noon on the date of birth.
In either case, the Sun is arbitrarily placed on the Ascendent, the eastern horizon, and 12 solar houses are calculated uniformly (equal house system) from that position.
Put your pencil and paper away. Most modern astrology software is only a mouse-click away from either method.
There are two major shortcomings in a solar chart:
1. The inaccuracy of the position of the Moon, the second most important planetary body in a chart (after the Sun); and
2. The complete absence of the natal house system.
Interpreting a Solar chart is like trying to play the Minute Waltz on the piano with one hand. There's a lot of notes which are going to be missed. In fact, it contains only about half the information of a full natal chart. This brings us to the sad reality that so much information is missing that it is very difficult for me to do a karmic reading using a Solar chart. However, astrologers of all flavours still use the Solar chart for one simple reason:
It's better than nothing.
Technical stuff a non-astrologer can skip:
For reasons of accuracy, my personal preference in a Solar chart is the 12 Noon calculation. That means the real Moon position is no more than ± 6° from the position given in the Solar chart. The other planets are always within ± 1° of their true position, which is reasonably satisfactory.
In a sunrise chart the Moon can be as much as 9° away from the real position, and the other inner planets could be as much as 2° away from their actual position.
Since accuracy of interpretation is directly dependent on accuracy of calculation, my view is these potentially larger discrepancies render the sunrise chart useless (oops, my Sun in Virgo is showing), which is why I prefer the 12 Noon solar chart. Non-Virgo astrologers are often comfortable with a sunrise solar chart.