Manual Bresser 9140400 National Geographic 40-400 (page 10 of 36) (English, German, Dutch, French, Italian, Polish, Spanish)

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The moon has been known to humans since prehistoric times. It is the second brightest object in the

sky, after the sun. Because the moon circles the Earth once per month, the angle between the Earth, the

moon and the sun is constantly changing; one sees this change in the phases of the moon. The time

between two consecutive new moon phases is about 29.5 days (709 hours).

Constellation Orion: The Orion Nebula (M 42)

Distance: 1,344 light years from Earth

Though it is more than 1,344 light years from Earth, the Orion Nebula (M 42) is the brightest diffuse

nebula in the sky. It is visible even with the naked eye and a worthwhile object for telescopes of all types

and sizes. The nebula consists of a gigantic cloud of hydrogen gas with a diameter of hundreds of light

years.

Constellation Lyra: The Ring Nebula (M 57)

Distance: 2,412 light years from Earth

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)

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 magnied still more.

There is a simple formula for calculating the magnication:

Focal length of the telescope tube / Focal length of the eyepiece = Magnication

In a telescope, the magnication 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 magnication:

400 mm / 20 mm = 20 times magnication

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Bresser 9140400 National Geographic 40-400 Manual

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