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
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
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
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.