ULTRAVISION

Ultravision is the ability to see radiation in the ultraviolet spectrum -- gamma rays, x-rays, etc.
Creatures with this ability can see in normal nighttime darkness; that is,
they see at night as well as a human can see at dusk because of the continual bombardment of ultraviolet radiation upon the earth.

** Ultravision (MU4, I2 - alteration)
** Ultravision (DMG)

Ultravision

Ultravision, or “night vision,” is the ability to see into the ultraviolet
range of the spectrum and thereby distinguish objects from
their surroundings even in darkness. In fact, the word “darkness”
takes on a different meaning for someone using ultravision:
He can distinguish colors, shapes, and the relative position
of objects even in the absence of light in the normal visible spectrum.
Only one character race, the deep gnome, has inborn ultravisual
capabilities. Such a character has night vision to a
range of 30 yards, meaning that objects within that range are visible
to him just as if he was using normal vision during daylight.
Other characters can acquire ultravision temporarily through
magical means, such as a lens of ultravision and the ultravision
spell, which can be cast by a magic-user or an illusionist. The exact
capabilities bestowed by magical ultravision (range and
amount of illumination perceived) vary depending on the means
employed.

As with infravision, this power is useless when the viewer or the
target is illuminated by any light source brighter than moonlight.
A character who tries to use ultravision in daylight or in an area affected
by artificial illumination will see nothing but blackness.
Ultravision works best during a moonless night under a clear
sky. When any of the following conditions exist, the range of ultravision
is affected accordingly:

Moonless night, partly cloudy: X 2/3
Moonless night, overcast: x 112
Moonlight, partly cloudy: x 113
Moonlight, overcast: X 114
Viewer standing under thick cover: X 114

The last of these modifiers is cumulative with any other modifier
that applies; thus, someone in the middle of a thick forest on a
moonlit, overcast night has ultravisual capabilities out to only 1/16
of the range he would have under ideal conditions.

- Wilderness Survival Guide