Bresser NATIONAL GEOGRAPHIC 50/360 Instrucciones De Uso página 10

The famous Ring Nebula (M57) in the Lyra constellation 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 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)
Right Ascension: 19 59 (hours : minutes) / Declination: +22° 43' (Degrees : minutes)
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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. An eyepiece captures and
magnifies the clear image that is generated in the focal point of a lens even more.
There is a simple formula for calculating the magnification:
Focal width of the telescope tube / Focal width of the eyepiece = Magnification
In a telescope, the magnification depends on both the focal width of the telescope tube and the focal width
of the eyepiece. From this formula, we see that if you use an eyepiece with a focal width of 20 mm and a
telescope tube with a focal width of 360 mm, you will get the following magnification:
360 mm / 20 mm = 18 times magnification
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 so that the light gives a clear image in the focal point after it
has traveled a certain distance (focal width).
Magnification:
The magnification corresponds to the difference between observation with the naked eye and observation
through a magnification apparatus (e.g. a telescope). Observation with the eye is considered 'single', or 1X
magnification. Accordingly, if a telescope has a magnification of 18X, then an object viewed through the
telescope will appear 18 times larger than it would with the naked eye. See also 'Eyepiece'.
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