Astronomically speaking, your first house is that one-twelfth sector of the local sky just below the eastern horizon occupied by planets two hours before they rise. Astrologically it symbolizes early childhood conditioning, and describes self-awareness and the experiences most necessary for its development. The first house is the mask you wear in relating to and projecting yourself into the world. It rules physical appearance, body type, conscious self-image, and how others see and experience you. It’s the window through which you view the world, and through which others receive their first impressions of you.

Whereas your first house is the window through which you view the world and through which others receive their first impressions of you, the sign on the cusp of your first house (your Rising sign) is the particular tint on the glass of that window, coloring and modifying all energy that passes into and out of your being. In fact, all of your personality functions (planetary energies) must eventually emerge through and be colored by your first house cusp if they are to emerge at all. Planets in the first house are parts of your self-expression. The more planets here (except Saturn and Neptune), the more you are involved with putting out your own energy rather than experiencing that of others, hence the greater your subjectivity. Thus the sign on your first house cusp conditions the way you look and how you express yourself.

First house Jupiter individuals tend to be both energetically and physically large people. Very generous, expansive and self-indulgent, you love travel, sports and pleasure, and attract abundance to you. The closer Jupiter is to your ascendant, the more pronounced are the foregoing attributes. Because Jupiter rules Sagittarius, sign qualities of Sagittarius other than those previously mentioned (such as a love of philosophy and freedom, extroversion, teaching, and religion) will also be accentuated, but will be somewhat diminished if Jupiter is in a sign other than your Rising sign. If Jupiter is afflicted, however, you need be careful of squandering resources, hypocrisy and self-centeredness.

If Jupiter is within 10° of the ascendant it is conjunct the ascendant, and much of the foregoing is even more strongly emphasized. If Jupiter is in the twelfth house AND within 4° or 5° of the ascendant, then it is said to be on the "dark side" of the first house, and it influence will be felt in the first as well as in the twelfth house. The closer a twelfth house Jupiter is to the ascendant, the more it will be interpreted as though it were in the first house; when less than 3° from the ascendant, a twelfth house Jupiter expresses itself primarily—and eventually entirely—in the first house.