Bresser Junior 76/300 SMART Compact Mode D'emploi page 10

Ring Nebula in Lyra constellation (M 57)
M 57 in the Lyra constellation
Distance: 2.000 light years
The famous Ring Nebula M 57 in the constellation of Lyra is often viewed as the prototype of a planetary
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 of a gas structure in the form of a sphere or an ellipsis.
If you were to look at the Ring Nebula from the side, it would look like the Dumbbell Nebula (M27). With
this object, we're looking directly at the pole of the nebula.
Dumbbell Nebula in the Vulpecula (Fox) constellation (M 27)
M 27 in the Fox constellation
Distance: 1.250 light years
The Dumbbell Nebula (M 27) in Fox was the first planetary nebula ever discovered. On July 12, 1764,
Charles Messier discovered this new and fascinating class of objects. We see this object almost directly
from its equatorial plane. If you could see the Dumbbell Nebula from one of the poles, it would probably
reveal the shape of a ring, and we would see something very similar to what we know from the Ring Nebula
(M 57). In reasonably good weather, we can see this object well even with small magnifications.
Telescope ABC's
What do the following terms mean?
Focal width:
Everything that magnifies an object via an optic (lens) has a certain focal width. The focal width 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 widths of the telescope tube
and the eyepieces are combined:
Lens:
The lens turns the light which 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 width).
Eyepiece:
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 width of the telescope tube / Focal width of the eyepiece = Magnification
You see: In a telescope, the magnification depends on both the focal width of the telescope tube and the
focal width of the eyepiece.
Magnification:
The magnification corresponds to the difference between observation with the naked eye and observation
through a magnification apparatus (e.g. a telescope). In this scheme, observation with the eye is considered
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