Pages 28 & 29, Street Grimoire.
ASTRAL SHALLOW
Astral shallows are places where the barrier between
the astral and physical space has become thin, allowing
even a mundane to use it like a window to perceive
the astral plane. While within the astral shallow, Awakened
people find astral perception to be easier, while
mundane individuals may look at astral forms as if they
had astral perception, though they cannot touch them.
Communication visually and audibly can be easily done
through an astral shallow. Astral shallows are normally
temporary in nature, lasting a few hours or days.
GAME INFORMATION
Astral shallows: Awakened people who can normally astrally
perceive can switch between astral and normal vision with
a Free Action instead of a Simple Action.
SAMPLE ASTRAL SHALLOWS
ABERDEEN AND FUZHOU SKY TOWER, HONG KONG
The unique construction and placement of the Wuxing
Sky Towers in Aberdeen and Fuzhou on intersecting mana
lines have allowed a permanent astral shallow to form
around both of them. Aberdeen’s shallow has grown up to
five kilometers in diameter, while Fuzhou Sky Tower’s is at
two kilometers in diameter.
TAJ MAHAL, INDIA
With the inhabitation of a great spirit at the Taj Mahal, the
emotional domain also became an astral shallow, allowing
many to believe they can see their deceased loved ones
walking the halls.
There is nothing indicating an astral shallow is a mana ebb or void. Nor is there any indication that it'd even have a background count. It's a thin spot, not a negative or drain.