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The
Basics of Astrophotography
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What
is astrophotography?
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HUTCHINSON Dictionary of science says... |
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"Astrophotography
is the use of photography in astronomical research."
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In
a scientific sense there is nothing wrong with this quote
but it is a bit strong in terms of what we need to use
as a reference. Other sources, non-scientific, call it
the "Photography of the night sky". That's
better. A nice, rounded, general term for us to use!
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Well... that's exactly
what it is. |
| Astrophotography
IS the photography of the night sky.
The image on the right IS an astrophotograph.
It IS a photograph, it WAS taken
at night and the camera WAS pointing
at the sky! |
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Photo
of Orion's Belt and Sword. The constellation
of Orion can be seen on any clear, winter
night. The three bright stars at the top
are the Belt and the three bright points
of light at bottom left are the sword. The
fuzzy point of light at the centre of the
sword is the Great Nebula.
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Different
kinds of astrophotography.
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There
are several ways in which photographs of the night sky can
be captured. The one we're interested in is the easiest and
by far the cheapest (depending on how serious you want to
get of course!) and that is by using a long exposure capable
camera atop a tripod.
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Other
ways of getting photographs of the night sky:
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Piggybacked
Camera - Attaching the camera to the back of a motor driven
telescope or tripod. |
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Through
a Telescope - Attaching the camera at the prime focus
of a telescope allowing the telescope to become the lens
of the camera. |
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What
you need to get started.
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The
essentials of astrophotography are simple and can be implemented
by adhering to this short but clear list:
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Clear
Skies |
If
the sky is full of clouds there is nothing to photograph.
Unless of course you like clouds! |
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Dark
Skies |
Light
pollution makes shooting the stars a difficult job from
the centre or even the outskirts of a city. Suburbia,
towns and villages are not much better, but they do allow
a bit more starlight through, enough to make out the major
constellations. The best bet is to get away from all the
street lights and head out into the countryside, but you
don't have to go far to just realise what a difference
it makes. |
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Camera |
Not
just any old camera. It must have a manual exposure or
'Bulb' setting. We will go into more detail about what
sort of camera to use in the equipment
section. |
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Tripod |
Camera
movement during long exposures is a big no no. The tripod
should be as sturdy as possible, but not too heavy to
carry. We will go into more detail about tripods in the
equipment section. |
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Fast
film |
The
faster the film speed the quicker light is captured upon
it. Film speed is its ISO rating (e.g. ISO 200 or ISO
400 etc.). We will go into more detail about film in the
equipment section. |
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Target |
Get
to know the night sky. Learn how to distinguish one constellation
or planet from another. You need to know what you are
photographing. Pointing the camera at the starry sky and
clicking will yield results but if you do not know what
you're looking at, the effort will be meaningless. |
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What
to photograph!
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Where
do I start? There is so much to shoot!
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Our
skies are full of so much beauty and there is so much choice
it may well be very difficult to decide where to start.
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that film is the cheapest commodity available to any photographer
so take loads of shots, at different exposure lengths and compare
the results. Most of the best camera on tripod astrophotographs
also include earth bound objects. Not always possible, but try
to include buildings of interest, trees, the line of a fence
etc.. This does mean, however, waiting until your chosen target
is close to the horizon so, unfortunately, there is more of
Earth's atmosphere for the light to penetrate through. |
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a bright target for your first shots. A constellation
with several bright stars like Orion or The Plough in
Ursa Major. These are probably the most famous of the
constellations and the easiest to recognise. Due to the
Earth's rotation, the stars near the ecliptic move across
the sky faster than those at the celestial poles. This
means, to prevent the stars trailing across your photographs,
a shorter exposure is required for constellations near
the ecliptic compared to those near the celestial poles.
The ecliptic constellations include all those of the Zodiac
and Orion. Those near the poles include Ursa Major, Cassiopeia
and Ursa Minor, which contains the North Star. |
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The
Planets and Planetary Conjunctions
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| Planets
and especially planetary conjunctions are another
good starting point. Some of the planets, like Jupiter
and especially Venus, are brighter than most of
the stars in the sky. The brighter planets
, Venus, Mars, Jupiter and Saturn, are easily recognisable
and quite easy to capture in panoramic views of
the night sky and when they appear in our skies
they are usually around for quite some time. Mercury
on the other hand is much more elusive. It never
rises very high in the sky and because it lives
so near the Sun, it is often lost in the twilight.
Planetary conjunctions are a spectacular sight.
Two, three, four and on occasion, but rarely, five
planets all together is the same part of the sky.
Always an added bonus is if a crescent moon can
be included in the shot. |
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| What
could be easier? Set up the camera, open the shutter
then just sit back and wait for the stars to stroll
across the sky. This
method will result in hundreds of lines across the
photo. A popular shot is of the circumpolar stars,
creating ever decreasing circles which can make
for a spectacular shot, especially if there is some
sort of foreground interest. For long star
trails a very dark site is required, well away from
light pollution. To test a sites usability try exposing
at several shorter periods, say 10, 20 and 30 minutes.
If your results are consistently dark, then the
site should handle a couple of hours of exposure. |
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using slower films like ISO 100 or 200, and stop
down the aperture to f 4 or f 8. Leaving
the shutter of a camera open for long periods of
time can however result in reciprocity failure.
Reciprocity failure can give contrast and colour
changes to film that will negatively impact your
photographs. |
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| Have
the shutter of a camera open long enough on the
night sky and sooner or later a meteor will stray
into frame. To increase these chances or to purposefully
capture meteors, take your camera out on the night
of a meteor shower. These come along several times
a year, some heavier than others. |
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| Several
times a Century, a comet that is visible to the
naked eye, traverses the Sun. When this happens
you will undoubtedly become aware as it will be
a newsworthy item. They may come quite close to
Earth and will outshine the planets but at other
times they will be quite diffuse and require very
dark skies and quite long exposures to capture them
well on film. |
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Auroras
(The "Northern (or Southern) Lights")
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you are lucky enough to live in northerly or southerly
latitudes, you will already be aware of the occasional
Auroras created by particles from the Sun hitting
our atmosphere. Intensity varies and the phenomena
is difficult to predict so timing and patience is
everything. Shorter exposures will show the rippling
effect of the lights where as longer exposures will
show colour intensity. |
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Astrophotography
Hints & Tips
Astrophotography
Definitions.
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