Bresser Junior 8840350 Mode D'emploi page 10

nebula. It is one of the magnificent features of the Northern Hemisphere's summer sky. Recent studies
have shown that it is probably comprised of a ring (torus) of brightly shining material that surrounds the
central star (only visible with larger telescopes), and not a gas structure in the form of a sphere or an
ellipse. If you were to look at the Ring Nebula from the side, it would look like the Dumbbell Nebula (M
27). When viewed from Earth, we are looking directly at the pole of the nebula.
Constellation Vulpecula (Little Fox):
The Dumbbell Nebula (M 27)
Distance: 1,360 light years from Earth
The Dumbbell Nebula (M 27) was the first planetary nebula ever discovered. On 12 July 1764, Charles
Messier discovered this new and fascinating class of objects. We see this object almost directly from its
equatorial plane. If we could see the Dumbbell Nebula from one of its poles, we would probably see the
shape of a ring, something very similar to what we know as the Ring Nebula (M 57). In reasonably good
weather, we can see this object well, even with low magnification.
Telescope ABC's
What do the following terms mean?
Eyepiece (3):
An eyepiece is a system made for your eye and comprised of one or more lenses. In an eyepiece, the clear
image that is generated in the focal point of a lens is captured and magnified still more.
There is a simple formula for calculating the magnification:
Focal length of the telescope tube / Focal length of the eyepiece = Magnification
In a telescope, the magnification depends on both the focal length of the telescope tube and the focal length
of the eyepiece. From this formula, we see that if you use an eyepiece with a focal length of 20 mm and a
telescope tube with a focal length of 400 mm, you will get the following magnification:
400 mm / 20 mm = 20 times magnification
Focal length:
Everything that magnifies an object via an optic (lens) has a certain focal length. The focal length is the
length of the path the light travels from the surface of the lens to its focal point. The focal point is also
referred to as the focus. In focus, the image is clear. In the case of a telescope, the focal length of the tel-
escope tube and the eyepieces are combined.
Lens:
The lens turns the light that falls on it around in such a way so that the light gives a clear image in the focal
point after it has traveled a certain distance (focal length).
Magnification:
The magnification corresponds to the difference between observation with the naked eye and observation
through a magnifying device like a telescope. If a telescope configuration has a magnification of 30x, then an
object viewed through the telescope will appear 30 times larger than it would with the naked eye. See also
'Eyepiece'.
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