P r i m a L u c e L a b S . p . A .
E A G L E C O R E U s e r M a n u a l
Connecting DSLR or mirrorless camera to telescopes
When we want to use a telescope to do astrophotography, we can connect the camera in various ways, thus
getting different magnification capabilities:
-
prime focus photography
: the camera body is directly connected to the telescope that is used as a powerful
telephoto lens. So if the telescope, for example, is a 80mm diameter refractor and 500mm focal length, we will
use it as a 500mm f6.25 telephoto lens. This type of use is usually applied to long exposure astrophotography of
galaxies, star clusters and nebulae, or in the low-magnification planetary/Moon one (for example, to photograph
the entire lunar surface as seen on page 83). The type of accessory required for prime focus photography
depends on the type of telescope we are connecting the camera to (so you have to read the telescope manual
before) but, if we consider the refractor telescopes, it is usually made with 2 accessories:
1- T2 or M48 ring that, connected in front of the camera body instead of the photo lens, converts the brand
bayonet into an universal 42x0,75 (T2) or 48x0,75 (M48) thread.
2- T2-50,8mm photographic adapter (or M48-50,8mm based on the ring previously used) that, threaded to
T2 ring, allows you to connect the camera to any telescope focuser (that usually has 50,8mm diameter)
Instead of the T2-50.8mm photo adapter, you can use a
field flattener
(or coma corrector) that does not change
the telescope focus. Some telescopes also offer dedicated
focal reducers
which, by reducing the focal length of
the telescope, also reduce the focal point and thus make it more "fast", making it easier to capture weak objects. It
should always be considered, however, that reducing the focal length of the telescope reduces the magnification
generated and thus also the resolution capacity of the telescope. So the use of a focal reducer is not always the
best solution for astrophotography.
Nikon DSLR camera connected in prime focus (with
field flattener) to apochromatic refractor: this way is
uses the telescope as a 650mm (f6.25) telephoto
lens
-
projection photography
: using special adapters, we use an optic element (which can be an
eyepiece
or a
Barlow lens
) between the camera and the telescope, and this is used to multiply the focal length and thus the
magnification generated by the telescope. This way, you can get images of lunar details (such as craters) and
planets of the Solar System. It should be considered that increasing the magnification, the focal ratio of the
telescope will also increase (for example, from f/6 to f/20) and therefore this technique is not suitable for
recording weak objects with long expositions.
Nikon DSLR camera connected with projection
(with 3x Barlow lens) to apochromatic refractor: this
way we use it at 650mm x 3 = 1950mm focal length
(f18.75)
page 26
