Yes, breaking the illusion is as simple as checking Astral. However, a careful GM is allowed to say: "Why are you checking Astral?" Remember that most magically awakened characters do not spend the majority of their time reviewing the Astral. Most of the time, they are firmly planted on the Physical. So, from an RP perspective, there should be a good reason for them to check the Astral.
- Maybe the character is on Magical Security, and checking every 5 minutes is in his job description.
- Maybe he has a Watcher Spirit who warned him: "There's a magically active person coming"
- Maybe there is some Astrally Active moss on the ground that you walked across, and it lit up.
There are some ways to get around this - some less effective than others:
- The Stealth skillgroup, or Infiltration skill, is technically effective on the Astral as well. So you can hide, and an opposing NPC/Character does need to defeat it.
- If you are using a likeness which is very close to your original appearance, then the Disguise skill would be applicable on the Astral. That is: An Assensing Test would not automatically detect a difference (they would actually have to be looking for it).
- The Metamagic Technique "Masking" will allow you to disguise your aura, at will, which allows you to match your aura to your physical appearance.
- The Metamagic Technique "Extended Masking" will also allow you to include the spell in your aura disguise, making it hidden as well.
That said: neither Infiltration nor Disguise will help with obvious differences. And Masking and Extended Masking can be defeated with a successful Assensing test (though the higher your Intiation Level, the more difficult that is to defeat). But, it's also much harder to increase the dice-pool for Assensing, and since you have to take Assensing in addition to Perception for the Astral, the available BP/Karma is often limited in increasing that particular dice pool.
