In astrology, the antiscion (pl. antiscia) is considered to be the mirror image, or shadow, of a planet based upon a line of reference, which is the axis of 0 Cancer/0 Capricorn. These antiscia are also known as the "solstice points".
The corresponding antiscia sign placements are as follows:-
A planet's antiscion is the shadow of that planet. A planet can receive a transit, progression, or direction from another planet, and this is said to bring about covert kinds of events—backroom meetings, secret doings, discreet happenings.
In order to calculate an antisca point, one must take the degree of the planet that he wants to locate the antiscia for and subtract it from 30 degrees. For example, if a person's sun is 10 degrees 51 minutes Aquarius then his antiscia will be as follows:-
Therefore, the antiscia of 10 degrees 51 minutes Aquarius is 19 degrees 9 minutes Scorpio.
Whenever a planet's antiscion is aspected by transit or progression, it indicates that something that is hidden or working behind the scenes will occur in the life of the native. It is important, therefore, that one should look at the antiscia points whenever reading a horoscope because it will reveal things about the native that will not be readily apparent.