highest ISO setting on the camera. You can use a lower
ISO setting to reduce the noise in the image, but you
will also lower the sensitivity and the number of stars
that can be recorded.
Focusing can be a little problematic as the lens
is to take images through a telescope. This is where the
is at the end of the focus movement . You need to set
the focusing mode into manual focus and turn off any
camera mounting to a generic lens. This is known as
a T2 mount and has the bayonet
on one
side with a thread inside.
The thread is used
to screw in an
eyepiece
adapter
resulting
in
a
sturdy
during the day on something as far away as possible
helps me get set up. A piece of electrical tape is your
friend here as it can be placed over the focus ring and
prevent movement. When night falls and you set up to
take your pictures there should only be a small amount
focus.
fore. Why not replace the lens with a telescope? The
mechanics of this is surprisingly easy. The camera lens
Computerised
Camera Control
If you want to get a bit more serious about
astrophotography and have a laptop and compatible
camera you can shoot in tethered mode. This is
where the computer controls the features of the
camera. Canon cameras are particularly useful for
this as there is a lot of software available, both
Commercial and Freeware, that can control the
entire imaging process. I still have my D300, but I
decided to get a dedicated astrophotography
camera, and after a lot of comparisons decided
to go for the Canon T3i a versatile workhorse
that could be fully controlled by my computer. I
also use APT - Astro Photography Tool a Freeware
imaging application. APT does far more than just
control the camera, but this is the area that I am
covering here. For more details about APT check
their website at www.ideiki.com.
Just above I mentioned the problems with focusing
at night. APT is able to control the camera lens and
can ever do manually. It also has a number of features
that assist in achieving focus including live view, lens
control, autofocusing, and focus aid. Using these tools
help you frame and focus your image. APT also has a
feature that allows you to program a sequence of shots
enabling you to automate the process of your night
work. I have just touched on the surface of what the
program can do and there are many other alternatives
out there that do the same thing. As each camera
offers different facilities check with the compatibility
purchase or acquisition.
Connecting
to a Telescope
alone camera, but a main concept of astrophotography
www.RocketSTEM .org
The bayonet
and nosepiece
of a T2 camera
mount adapter.
Credit: Mike Barrett
connection
between
the
camera
and the telescope.
The telescope then becomes a long focal length lens.
There are a couple of drawbacks to using this
method for connecting a camera to a telescope. The
main problems are backfocus and star trailing.
Backfocus in astrophotography is the ability of the
on the body indicating where the sensor is. This is also
the focus point of the camera. An eyepiece has it’s
focal point some way below the eye, but a camera
has it above the plane where your eye would be. This
means that the telescope focuser has to be able to
move in far enough for the camera to achieve focus.
This is normally not a problem with a refractor telescope
by using a Barlow lens which shifts the focus point and
can allow the camera to achieve focus.
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