Current night-sky
view (nighttime operation only).
Click image for full-sized version.
During the local hours of darkness, the EPSO all-sky camera
takes a continuous series of 60-second exposures showing a
full-hemisphere horizon-to-horizon colour image of the local
night sky. Imaging starts at 45 minutes after sunset and
stops at 45 minutes before sunrise, during which time there
are automatic Web image uploads every 10 minutes.
Passing aircraft, meteors and satellites will show up as lines
on the image. Aircraft
trails may present as a series of dots from the flashing
of their anti-collision strobe lights, whereas satellites
trails tend to be of more uniform illumination except where
the satellite may be tumbling. Meteors are generally of
shorter length and may show variable
brightness along the trail as the meteor burns up or
breaks apart. Sometimes it can be tricky to positively
identify what's what, but fortunately there are handy tools to
check what's flying around overhead, most notably Heavens
Above and Flightradar24.
Both are excellent, and lately Flightradar24 has added a
feature to look back in time so that one can check whether
aircraft were in the local area.
The EPSO camera is run by the control software AllSkEye,
which at dawn compiles all the night's 60-second images
together to make a movie,
and also stacks the images together to show star-trails
for the night. For those who might wish to make
their own all-sky camera system, AllSkEye is outstandingly
well written software.
The primary motivation for operating this camera is capturing
meteor trails, or 'fireballs'
as very bright trails are known, but lots of other curious
things are picked up along the way. One such thing is a
flashing satellite, where the satellite (usually a large piece
of space junk) is tumbling it its orbit, causing the brightness
of the reflected sunlight to vary. On very rare
occasions one might catch part of the launch sequence of a
large rocket, such as the post-launch fuel
dump (in orbit) from a Centaur rocket (on the EPSO
all-sky this event presented as a fuzzy
blob moving against the starry background). Fairly regularly, the passage
of the International Space Station will appear as a
very bright light traveling across in the dawn and dusk
skies. Similarly, recent launches of clusters of Starlink
satellites can present quite a visual spectacle for a naked
eye observer. On all-sky camera images these trails
take the appearance of an aircraft
contrail until closer inspection of the image reveals
that it is made up of many individual trails. For
example, the addition of 46 new Starlink satellites by the Starlink
G3-1 launch on the 11th July, 2022 (UTC), showed
up very prominently in the dawn sky on the 13th July
(UTC). Close inspection of this time-lapse trail shows
many individual trail-lines.
Often the whole all-sky image takes on a distinctly green or red
colour, being emissions known as airglow.
Similarly one may occasionally see distinct
moving patterns of glow, being caused by the passage of
atmospheric
buoyancy waves in the Earth's mesosphere.
Tidal
winds propagating vertically in this region can blow
meteor smoke trails into interesting shapes. One such
event captured by the EPSO camera shows a near-vertical meteor
trail which is then gradually blown around to form a curious
expanding ring
shape in the sky.
On the 15 January 2022, an undersea
volcano located nearby the pacific island of Tonga erupted,
causing the biggest atmospheric explosion ever recorded with
modern instrumentation, and launching hundreds of thousands of
tonnes of gas and dust as high as 60km into the
atmosphere. Around a month later, on the 14th of
February, the EPSO camera recorded extraordinary
vivid sky colours during the sunrise and sunset
twilights. Coincidentally I was awake early on
this day and was surprised to see dawn twilight starting
around 30 minutes earlier than normal, due to sunlight
reflecting from dust that was circulating much higher in the
atmosphere than normal. Since that time the twilight sky
colours have looked generally different, sometimes distinctly
purple and sometimes 'apricot' in colour. An image
showing all-sky thumbnail images for the first of 2022,
shows how sunset colours have changed during that
period. These images may also be viewed as a movie.
