Uranus
Through The Telescope (click
for animation, 4 KB)
For
most telescopic observers, Uranus presents a somewhat disappointing
sight (click thumbnail for full animation, 4KB). All that can normally be seen is a small, pale blue-green
disk showing no detail. Larger telescopes will reveal its five brightest
moons, which are (in order of descending
opposition magnitude) Titania (magnitude +13.7),
Oberon (mag. +13.9), Ariel (mag. +14.2), Umbriel (mag.
+14.8) and Miranda (mag. +16.3).
For useful observation of the planet, telescopes of at least 8 inches (200mm)
aperture and magnifications of 300x or more are generally considered necessary.
Even
through large telescopes the planet often appears fuzzy and indistinct. Brightness variations are sometimes reported, the
likely result of changes in the planet's atmosphere. In particular,
observers have reported a light banding across the planet's equatorial
region (whenever this is on view - of which, see below). Overall,
Uranus
will appear to brighten slightly at each successive opposition through
to its perihelion in 2050.
Because
of Uranus' unusual axial tilt (98° relative to the plane of its orbit) it presents very different aspects when seen from
the Earth. In the course of its 84-year orbit around the Sun, it
variously appears pole-on to the Earth, sideways-on, or somewhere
in-between. Its equator was last seen face-on to the Earth in December
2007; its South Pole will appear face-on to the Earth in 2030.
When mounted on
a tripod, digital cameras fitted with a zoom lens will easily detect the
planet at shutter speeds of only a couple of seconds at higher ISO (film speed)
settings. Some photos will even reveal the characteristic
colouration of the planet.
The
images of the planet seen here were taken using a DSLR camera
pointed through the eyepiece of an 8-inch reflecting telescope in
2006. The rippling effect simulates how the Earth's turbulent atmosphere
(the 'seeing conditions') affects the steadiness and clarity of the telescopic image.
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