Yes it's possible,
But you need more concentration because sometimes other factors may alter the circle existence. Try practicing it in the astral world before your attempt to actually use it in your mind. Also use any kind of divination you know how to use to feel if it's alright to make a circle at such time.
there is many ways to find north or south, try this one:
Face the sun rise and you will find north at your left.
Face the sun set and you will find south at your left.
Re: Casting a circle
By: Lark Moderator / Knowledgeable Feb 26, 2014
Post # 4
It's absolutely possible for you to cast a circle in your mind. For that matter, even when we cast a circle using tools the thing that really makes a circle work is that we have the focus and intent in our minds. So you could say that a circle is always cast in our minds, just that sometimes we use tools as well.
To tell where the cardinal points are simply pay attention to where the sun rises and sets where you live. The sun rises in the East and sets in the West so you have two directions identified right there. If you are facing the sun early in the morning as it rises, then North will be to your left and South to your right.