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Field Atlas · Vol. 406

AZIMUTHOptical Sky Phenomena

A field atlas of the sky's rarest optics — six phenomena, catalogued and card-bound. Each cover turns in real perspective to its field notes.

Northern & polar latitudes Photographed in the field Six specimens

Turn a card — hover, or focus it and press Enter / Space.

The Collection

06 / plates · rev. 406

Green aurora ribbons rippling over a dark starfield
01
Boreal

Aurora Borealis

Ribbon of ions

Field notes · 01

Aurora Borealis

Solar wind strikes oxygen and nitrogen high in the thermosphere and the sky answers in green. Hunt it on cold, moonless nights, far from the sodium glow of towns.

Altitude
90–400 km
Best season
Sep – Mar
Latitude
65°–72° N
Rarity
Log a sighting
A pale twenty-two degree ring encircling a hazy sun in a blue sky
02
Cirrus

22° Halo

The cold ring

Field notes · 02

22° Halo

Sunlight refracts through hexagonal ice crystals adrift in cirrus and bends exactly twenty-two degrees, tracing a pale ring. A quiet omen of the weather turning.

Altitude
5–10 km
Best season
All year
Radius
22° from sun
Rarity
Log a sighting
Electric-blue noctilucent cloud filaments over a deep twilight horizon
03
Mesosphere

Noctilucent

Night-shining clouds

Field notes · 03

Noctilucent

The highest clouds on Earth — seeded on meteoric dust and lit by a sun already set. Electric-blue filaments that surface only in the deepest summer twilight.

Altitude
~83 km
Best season
Jun – Aug
Latitude
50°–70°
Rarity
Log a sighting
A setting sun crowned by a thin green rim over a calm sea horizon
04
Marine

Green Flash

The last green

Field notes · 04

Green Flash

For a held breath at the sun's final edge, the atmosphere sorts light by colour — and the last to leave is green. Blink, and the day keeps it.

Duration
1–2 sec
Best time
Clear sunset
Horizon
Low & flat
Rarity
Log a sighting
A low winter sun flanked by two bright sun dogs on a faint halo arc
05
Parhelion

Sun Dogs

Twin suns

Field notes · 05

Sun Dogs

Plate-shaped ice crystals settle flat and mirror the sun sideways, hanging two bright ghosts at its shoulders. Brightest when the sun rides low over frozen ground.

Altitude
5–10 km
Best season
Winter, low sun
Angle
22° aside
Rarity
Log a sighting
Pastel iridescent mother-of-pearl clouds glowing at twilight
06
Stratosphere

Nacreous

Mother of pearl

Field notes · 06

Nacreous

Rare polar stratospheric clouds diffract the low sun into shell-like iridescence. Beautiful — and a fingerprint of the ozone layer's coldest, strangest chemistry.

Altitude
15–25 km
Best season
Deep polar winter
Temp
below −78 °C
Rarity
Log a sighting