1. It is clear that magic in this edition is almost always obvious and doesn't require a test to notice at all (that you only need to take a test if magic is subtle to begin with).
SR5 p. 280 Perceiving Magic
Magic is rarely subtle...But if the magic is subtle, then you have to pick up some dice.
2. It is clear that the victim of a subtle manipulation spell can notice it.
SR5 p. 292 Manipulation Spells
A victim of mental manipulation spell may roll to notice the magical effect according to the usual rules for Perceiving Magic (p. 280). Some of the less subtle mental spells (Control Actions) are pretty obvious, but more subtle spells (like Control Thoughts) can be pretty insidious.
3. It is clear that mundanes in this edition can notice when an astral form passes through their aura.
SR5 p. 314 Astral Detection
Physical beings may sense when an astral form passes through their aura.
4. It is clear that anything active on the astral plane in this edition have an astral form.
SR5 p. 312
Anything active on the astral plane, including spirits, active foci, dual-natured beings, etc., has a tangible astral form.
SR5 p. 319 Foci
While activated, a focus also has an astral form.
SR5 p. 280 Magical Ldoges
Then spend a number of days equal to the lodge’s Force dedicating the space, setting up the physical components, building its astral form, setting up barriers, and harmonizing it to your aura.
SR5 p. 301 Spirit Basics
Spirits are naturally astral forms, much like you’re naturally a physical form.
5. It is clear that spirits in this edition cause the air to shimmer (which mundanes can notice).
SR5 p. 280 Perceiving Magic
Spirits sometimes cause the air to shimmer, even from astral space
6. It is clear that you in this edition can notice magic that is being cast
SR5 p. 280 Perceiving Magic
Sometimes it’s obvious through a magician’s gestures or incantations (magicians seen by non-Awakened people are sometimes called “twitchy fingers”).... For example, if a magician with Spellcasting 6 casts a Force 4 manabolt, the threshold for spotting her do it is 2 (Skill Rating 6 – Force 4).
7. It is clear that you in this edition can notice when magic is in the area
SR5 p. 280 Perceiving Magic
People have reported feeling chills, dread, or other unnatural sensations they can’t quite put their finger on when magic is in the area.
8. It is clear that mundanes in this edition can specialize in noticing magic
SR5 p. 314 Astral Detection
Security personnel are trained to recognize this feeling as a sign of an astral intruder. This specialization of Perception is called Numinous Perception, which includes both the chilly tingle of astral forms and the “bad vibes” of noticing magic (p. 280).
In this edition it is not clear that a sustained spell would be impossible to notice.
edit to rephrase my comments from "sometimes" to "can"