What is being displayed here?
This dynamic
page is intended to demonstrate the
power that can be embedded within a
web page, by inserting some
additional program code that your
browser can understand (Java
Script). Because of an interest in
Astronomy, I have chosen to use some
calculations to show the
actual positions of the Sun, Moon
and planets as they are NOW
with respect to my telescope
position in Ewelme. Although the
results are accurate from here and
have involved some quite complex
algorithms, they are probably
perfectly adequate for the area of
Buckinghamshire, Berkshire and
Oxfordshire or even wider.
To make this information as
practically useful as possible, I
have just shown the Azimuth (compass
direction) and Altitude (angle above
the horizon). Both these angles are
shown in a rounded decimal degrees
form, although astronomers often
prefer these to be shown in degrees,
minutes and seconds. However,
unless one is using this real time
data to control the position of a
telescope, the whole degrees part
should be quite enough for just
trying to identify whether a bright
point in the night sky is a planet
or a star.
Either use a compass to find the
Az angle shown with respect to North
(0 degrees), or orientate yourself
using the North 'pole' star
(Polaris), remembering that East is
900.,
South is 1800.,
and West is 2700,
As far as Alt is concerned, remember
that 00
is the horizon and 900
is directly above your head. I'm
sure you'll realise that if a
reading is negative, it is below the
horizon, but you should be able to
deduce whether the object is tending
towards rising (-90 to 0) or has
just set (0 to -90).
Points of Interest
When the Moon phase = 100 %, the
moon is full. 0% is a new moon.
Between 0 and 100 the Moon is waxing
(getting lighter from right to
left), and between 100 and 0, it is
waning (getting darker from right to
left)
Because Venus (and Mercury)
orbits between the Earth and Sun, it
also goes through phases, which can
be recognised using a small
telescope.
"Midday" is usually recognised by
the fact that the Sun is at its
highest point in the sky (crosses
the Meridian = South). See what time
the Altitude of the Sun reaches its
maximum before falling towards zero
again (sunset). You might be
surprised that because we are at a
longitude of about 1 degree West, we
see this occur 4 minutes before 12
o'clock, because midday at Greenwich
(GMT) is really 4 minutes late in
Ewelme!!
The Sun is said to rise in the
East (90 degrees) and sets in the
West (270 degrees). This is in fact
so, when the day equals night
at the Spring and Autumn Equinoxes.
Notice that at other times, the sun
rises North of East and sets North
of West during the Summer (longer
days) and rises South of East and
sets South of West during the Winter
(shorter days). It reaches its
extremes at the Summer and Winter
Solstice.
At midday (-4 mins) on the day of
the Summer Solstice (mid summer)
the Sun will be at its annual
highest. In fact it will be at the
same angle as our Latitude here in
Ewelme i.e. 51.6 degrees.
The apparent path the Sun takes
across the sky is called the
Ecliptic, but remember that it is
the Earth orbiting a 'static' Sun
which actually gives this effect.
Since the planets, including the
Earth and Moon, all orbit the Sun in
about the same plane, it means that
they basically all follow the path
of the Ecliptic as well. So,
don't expect to see the Moon or any
of the planets if you are facing
North. However, there is a wonderful
'photograph' being sold locally of
the 'Dreaming Spires' of Oxford,
taken from South Parks looking
North. Above the domes and towers a
full moon completes this attractive
scene! That devious
photographer obviously hadn't read
these notes!
Advanced data